The owner of a convenience store near Salt Lake City in Utah has been tabulating weekly sales at the store, excluding gas. The accompanying data file contains the sales for 30 weeks. a. Use the 3-period moving average to forecast sales for the 31st week. Note: Do not round intermediate calculations. Round final answer to 2 decimal places. y^t= b. Use simple exponential smoothing with a=0.3 to forecast sales for the 31 st week. Note: Do not round intermediate calculations. Round final answer to 2 decimal places. y^t= c-1. Report the performance measures for the techniques in parts a and b. Note: Do not round intermediate calculations. Round final answers to 2 decimal places. c-2. Which is the preferred technique for making the forecast