I need help with the answers and can you show me the right formula used in excel by breaking it down for me in excel?

a. Construct a time-series graph of the sales data for HeathCo's line of skiwear (see data in c5p11 ). Does there appear to be a seasonal pattern in the sales data? Explain why you think the results are as you have found. (c5p11 () ) b. It seems logical that skiwear would sell better from Oetober through March than from April through September. To test this hypothesis, begin by adding two dummy variables to the data; a dummy variable Q1=1 for each first quarter (January, February. March) and Q1 =0 otherwise; and a dummy variable Q4 =1 for each fourth quarter (October. November, December) and Q4=0 otherwise. Once the dummy variables have been entered into your data set. estimate the following trend model: SAIESb0+b1(TIME)+b2QI+b3Q4 Evaluate these results by answering the following: - Do the signs make sense? Why or why not? - Are the coefficients statistically different from zero at a 95 percent confidence level (one-tailed test)? - What percentage of the variation in SALES is explained by this model? c. Use this model to make a forecast of SALES (SF2) for the four quarters of 2017 and calculate the MAPE for the forecast period. d. Prepare a time-series plot of SAIES (for 2007Q1 through 2016Q4) along with SF2 (for 2007Q1 through 2017Q4 ) to illustrate how SAI.SS and SF2 compare