Hello, Experts - Please solve this question.

Data set here>>

Store ID	Sales	Quarter	Prom
2683	143	3	0
2069	62	3	0
2465	249	2	0
2288	161	1	0
2383	40	1	0
1794	281	1	1
1921	258	3	1
2374	415	4	1
2130	113	3	0
1730	226	2	0
2149	124	2	0
1820	225	1	1
1864	145	1	0
2374	466	2	0
2796	192	2	0
2279	85	2	0
2284	140	2	0
2412	59	1	0
2258	89	1	0
1810	170	1	0
2557	138	2	0
2056	87	1	0
2212	223	4	0
2043	95	1	0
1758	177	2	0
1924	565	2	1
1730	165	4	0
1921	298	4	0
2806	269	2	0
1750	259	1	1
2235	114	2	0
2143	124	2	0
2143	137	4	0
1780	176	1	0
1764	259	1	1
2225	56	1	0
2829	223	1	1
2026	98	1	0
2684	366	4	1
2231	206	2	0
2026	122	4	0
2235	73	1	0
2326	91	1	0
2635	101	3	0
2465	134	3	0
2644	286	2	0
1780	347	4	0
1863	142	3	0
2035	127	2	0
1863	116	1	0
2764	225	2	0
2048	85	3	0
2283	116	1	0
2052	83	4	0
2385	57	1	0
2808	95	4	0
1722	212	4	0
2048	129	2	0
1718	78	1	0
2714	99	3	0
1864	182	2	0
2056	98	2	0
1760	251	2	0
2664	395	4	1
2415	95	3	0
1998	163	4	0
2855	135	1	0
2829	137	3	0
2309	92	1	0
2480	65	4	0
2677	48	4	0
2764	106	1	0
2114	329	4	0
2020	81	4	0
1750	401	3	0
1758	164	1	0
2069	109	2	0
2077	163	2	0
2231	127	1	0
2064	435	4	1
1998	189	3	0
2283	210	3	1
2104	225	2	0
2064	243	3	0
1730	130	1	0
2473	142	4	0
2335	54	1	0
2415	185	4	0
2674	146	4	0
2331	116	3	0
1764	508	3	0
1760	235	4	1
2674	127	2	0
2825	74	1	0
2077	80	1	0
2305	233	2	0
2029	121	1	0
2764	197	4	0
2383	97	4	0
2453	184	2	0
2902	116	4	0
1750	429	2	1
1718	173	3	1
2077	70	3	0
2114	207	2	0
1750	424	4	1
1850	141	2	0
1824	433	2	1
2283	336	2	1
1924	408	4	1
1722	156	1	0
2279	92	4	0
2309	192	4	0
1780	272	2	0
1794	932	2	1
2043	87	3	0
2043	185	4	0
2855	168	4	0
2226	57	3	0
2684	143	1	0
2533	30	1	0
1998	233	2	0
1760	133	1	0
2684	148	3	0
1722	171	3	0
1824	323	3	1
2664	235	3	0
2694	317	2	1
2683	188	4	0
1773	187	2	0
2104	107	1	0
2196	94	2	0
2315	97	1	0
2683	98	1	0
2385	140	4	0
2714	71	1	0
1850	125	4	0
2825	174	4	0
2035	160	4	0
2374	372	3	1
2854	312	2	0
2677	73	3	0
2624	238	3	1
2130	144	4	0
2383	78	2	0
2829	221	2	0
2674	71	1	0
2760	114	3	0
2453	178	3	1
2820	163	2	0
2335	179	2	0
2331	149	4	0
2226	169	2	0
2279	124	3	0
2714	174	4	0
1820	360	2	1
2557	92	4	0
2412	104	4	0
1764	660	2	1
2644	295	4	0
2390	101	3	0
2052	45	1	0
2854	146	1	0
2760	90	1	0
1985	104	2	0
2284	146	4	0
2806	209	4	0
2624	324	4	0
1864	145	3	0
2933	301	1	1
2241	58	3	0
2677	40	1	0
2624	340	2	0
2389	236	2	0
2933	416	4	1
2335	120	3	0
2241	96	2	0
2335	134	4	0
2412	148	2	0
2677	125	2	0
2473	63	1	0
2382	117	4	0
2374	188	1	0
2654	373	2	1
1758	154	3	0
1794	802	3	1
2805	220	4	0
1985	166	4	0
2112	86	1	0
2664	363	2	1
2326	91	4	0
2104	236	4	0
2225	83	3	0
1978	247	4	0
2654	343	4	0
1921	141	1	0
2241	53	1	0
2683	212	2	0
2048	76	1	0
1773	72	1	0
2644	128	1	0
2279	59	1	0
2241	104	4	0
2064	385	2	0
2557	90	1	0
2130	145	2	0
2331	85	1	0
2212	204	2	0
2305	88	1	0
2331	191	2	0
2050	306	2	1
2808	114	2	0
2933	656	2	0
2284	110	3	0
2392	147	3	0
2415	145	2	0
2415	102	1	0
2043	168	2	0
1978	399	2	1
1978	337	3	0
1730	214	3	0
2796	214	4	0
2674	103	3	0
2149	151	3	0
1810	272	3	1
1824	186	1	0
2760	123	4	0
2465	143	1	0
1810	337	4	0
2288	199	3	0
2412	156	3	0
2035	73	1	0
2149	94	4	0
2026	128	3	0
1773	216	4	0
2064	184	1	0
1794	562	4	1
2052	96	2	0
2290	227	2	0
1894	339	2	0
2806	196	3	0
2840	75	1	0
2315	137	2	0
2385	90	3	0
2288	115	4	0
2806	138	1	0
2465	145	4	0
2114	101	1	0
2143	88	3	0
2226	107	4	0
2226	52	1	0
1760	211	3	0
2389	231	4	0
2820	141	3	0
2808	50	1	0
2533	74	3	0
2664	131	1	0
2796	151	3	0
2829	199	4	0
2283	217	4	0
2149	69	1	0
2315	107	3	0
2290	148	4	0
2326	82	3	0
2840	130	3	0
1924	284	1	1
2258	100	2	0
2820	66	1	0
2258	79	3	0
2390	283	4	0
1978	189	1	0
2694	175	3	0
2029	234	4	0
2382	84	1	0
1894	145	1	0
1998	161	1	0
1924	542	3	1
2533	90	2	0
2694	333	4	0
2112	204	4	0
1718	152	2	0
2902	194	2	0
2143	35	1	0
2533	148	4	0
2020	66	1	0
2635	163	2	0
1921	285	2	0
2624	152	1	0
2225	118	4	0
2933	452	3	1
2284	42	1	0
2290	110	3	0
2048	93	4	0
2288	238	2	0
2453	134	4	0
1863	275	4	0
2212	103	1	0
2069	74	4	0
1820	310	4	0
2840	128	2	0
2114	156	3	0
2050	295	4	0
2392	98	1	0
2383	59	3	0
2840	159	4	0
2069	36	1	0
2805	162	3	0
1722	198	2	0
2389	182	3	1
2392	180	4	0
2694	142	1	0
2020	38	3	0
2020	128	2	0
2480	124	2	0
2480	50	1	0
2235	170	4	0
2796	116	1	0
1985	64	1	0
2644	189	3	1
2231	107	4	0
2473	79	3	0
2902	96	3	0
2902	99	1	0
2309	253	2	0
2453	72	1	0
2196	65	3	0
2112	186	3	0
2473	95	2	0
2056	132	4	0
1758	195	4	0
2035	109	3	0
2854	262	4	0
2760	146	2	0
2480	68	3	0
2196	69	4	0
2684	280	2	0
2805	234	2	0
2029	220	2	0
2557	102	3	0
2855	157	3	0
1850	89	1	0
2385	135	2	0
2628	120	4	0
2714	103	2	0
2305	143	3	0
1850	119	3	0
2231	149	3	0
2290	76	1	0
2628	142	3	0
2805	139	1	0
1820	275	3	1
1824	447	4	1
2050	144	1	0
2258	100	4	0
2382	159	2	0
2050	202	3	0
2326	155	2	0
2104	168	3	1
2808	71	3	0
1718	128	4	0
2855	132	2	0
2130	79	1	0
2392	176	2	0
2635	49	1	0
2305	213	4	0
2390	227	2	0
1894	277	3	0
2052	83	3	0
2628	69	1	0
2029	201	3	1
2820	172	4	0
2309	229	3	1
2628	98	2	0
2315	137	4	0
1863	250	2	0
2077	123	4	0
2225	120	2	0
2825	198	2	0
2235	119	3	0
2112	209	2	0
2635	183	4	0
2390	78	1	0
2382	104	3	0
2654	243	3	0
1764	590	4	1
1780	281	3	1
1894	237	4	0
1864	169	4	0
2056	92	3	0
2212	188	3	0
2026	145	2	0
2654	180	1	0
2196	70	1	0
1985	77	3	0
1810	369	2	0
2825	95	3	0
1773	129	3	0
2854	148	3	0
2764	289	3	1
2389	124	1	0

Given Quarterly sales data of work T-shirts from a sample of 100 stores belonging to a large Retailer. The first column is simply a store-id (STOREID), second column contains the quarterly sales in number of T-shirts sold (SALES), the third column gives you the quarter to which these sales belong (QUARTER) and finally the fourth column tells you whether the T-shirts were on promotion or not (PROM) [PROM = 1 implying that the T-shirts were on promotion].

(a) Run a regression with SALES as your dependent variable and QUARTER & PROM as your independent variables. Note that QUARTER is a categorical variable so you need to introduce appropriate dummy variables to represent it, choose the 4th quarter as your reference when you introduce dummy variables. That is, estimate the following regression model SALES = B0 + B1QTR1 + B2QTR2 + B3QTR3 + B4PROM where QTR1, QTR2, QTR3 are dummy variables for the first, second and third quarters respectively.

Report and interpret the estimated coefficient on QTR1

(b) Based on the estimated regression model in part (a) what is your estimate of the second quarter sales with and without promotions?

(c) What is the impact of promotions on sales?