A textbook publishing company has compiled data on total annual sales of its business textbooks for the preceding eight years: \begin{tabular}{lllllllll} Year: & 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 \\ Sales (000): & 38.20 & 43.80 & 48.60 & 51.30 & 56.30 & 59.70 & 62.40 & 69.90 \\ \hline \end{tabular} a-2. Forecast the preceding eight years, and determine the forecast errors. (Negative answers should be indicated by a minus sign. Do not round intermediate calculations and round your final answer to 2 decimal places.) a-3. Construct 2s control limits. (Round the final answer to 2 decimal places.) 2s control limits are b. Using the model, forecast textbook sales for each of the next five years. (Round the final answers to 1 decimal place.) c. Suppose actual sales for the next five years turn out as follows: Calculate the forecast errors for years 9 to 13 . Is the forecasting process in control