Jethro used his top$-$secret forecasting method to provide a forecast for the first six months of the year. Take a look at forecasted and actual demands below: NOTE: You will need to show ALL calculations $$ deviations, RSFE, Absolute Deviation, Sum of Absolute Deviations, MAD, and the Tracking Signal. Forecasted Actual Demand July $11201070$ August $13401290$ September $14901470$ October $12001120$ November $13101260$ December $13901300$ a$.$ Find the MAD and the Tracking Signal $($provide math or Excel file$)(30$ pts$)$ b$.$ Based on the Tracking Signal, tell me if you think Jethro$$s top secret method is accurate and WHY.