Please help me with the below. I previously asked the question on here but want to check I have done part a right. Part b, I am really struggling with. I can not figure out how MAD is calculated. I've seen answers for part b online, but no thorough explanation. Every time I calculate it, I do not get the same answer as the ones given on CourseHero. Really appreciate any help/explanation.

Q1												10 Marks		Sales
														Month	Sales	2 Months	St. Error	3 Months	St. Error
a) Develop the 2-months and 3-months moving averages for the supermarket sales.						1	125	#N/A	#N/A	#N/A	#N/A
Note: use data analysis tool pack.								5 Marks			2	141	133	#N/A	#N/A	#N/A
														3	125	124	5.70088	129.6667	#N/A
b) Which moving average appears to provide more accurate forecasts based on MAD? Explain.					4	123	124.5	1.27475	124.6667	#N/A
Note: show your MAD calculations.								5 Marks			5	126	135.5	6.80074	131.3333	8.812869
														6	145	146	6.75463	139.3333	9.079892
														7	147	154.5	5.35023	151.3333	10.9443
														8	162	158.5	5.85235	154.6667	7.586538
a) answer on the right													9	155	156.5	2.69258	158.3333	6.164414
														10	158	152.5	4.03113	153.3333	3.666667
														11	147	153	5.75543	154.6667	4.434712
														12	159