The classified department of a monthly magazine has use a combination of qualitative and quantitative methods to forecast sales of advertising space. results over a 20 month period are as follows. Month Error 1 -8 2 -2 3 4 4 7 5 9 6 5 7 0 8 -3 9 -9 10 -4 11 1 12 6 13 8 14 4 15 1 16 -2 17 -4 18 -8 19 -5 20 -1 a). compute a tracking signal for months 11 through 20. compute an intial value of MAD for month 11, and then update it for each month using exponential smoothing of alpha =.1. what can you conclude assuming limits of plus or minus 4. b). using the first half of the data, construct a control chart with 2s limits. what is the implication of this?