The question is below.

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: Month Error Month Error - 5 11 1 - 3 12 7 13 10 14 18 19 -4 20 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 = .4. (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.) Month The initial MAD Tracking signal 11 12 13 14 15 16 17 18 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 b-2. What can you conclude? Only the error for month 5 is outside of the limits. All errors are within these limits. Only the error for month 9 is outside of the limits