Pleas explain step by step.

Check my work 4 Problem 3-30 (Algo) The classified department of a monthly magazine has used a combination of quantitative and qualitative methods to forecast sales of advertising space. Results over a 20-month period are as follows: 5 points Month Error Month Error 1 -5 11 4 2 -3 126 3 3 13 8 4 6 14 4 5 13 152 6 3 16 -4 7 -1 17 -4 8 -5 18 -8 9 -8 19 -5 19 -4 26 -3 eBack Print References Click here for the Excel Data File a. Compute a tracking signal for months 11 through 20. To do so, compute an initial value of MAD for month 11, and then update it for each month using exponential smoothing with a = 1. (Leave no cells blank - be certain to enter "0" wherever required. Negative values should be indicated by a minus sign. Round your intermediate calculations and final answers to 3 decimal places.) t Month The initial MAD Tracking signal 4.636 1.078 11 12 13 14 15 16 17 18 Check my work 4 Click here for the Excel Data File a. Compute a tracking signal for months 11 through 20. To do so, compute an initial value of MAD for month 11, and then update it for each month using exponential smoothing with a = 1. (Leave no cells blank - be certain to enter "0" wherever required. Negative values should be indicated by a minus sign. Round your intermediate calculations and final answers to 3 decimal places.) 5 points t Month Book The initial MAD Tracking signal 4.636 1.078 11 12 13 Print 14 o 15 References 16 17 18 19 20 b-1. Using the first half of the data, construct a control chart with 2s limits. (Round your intermediate calculations to 3 decimal places and final answer to 2 decimal places.) Control limits 01 16.44