A local quick-service restaurant needs to forecast the weekly demand for its signature sandwich, which is on its menu. The demand, by week, for the signature sandwich for the first three weeks of the month was: first week 1391; second week 1421; and third week 1349. Showing all work, use a simple two-week moving-average to forecast for the restaurant's signature sandwich for the fourth week of the month. As part of your calculation, please show all work including; 1. Formula used. 2. Numerical values used in the formula. 3. Final (calculated) forecast.