a$)$ Use two$-$ month average and use trend projection method to forecast the coal sales. Based on the analysis in part $($A$)$ and $($B$),$ which method moving average, or trend projection provides better forecast

$$

Weather Index

Coal Sales $($Millions of Tons$)$

X

Y

$$

$$

$2$

$4$

$1$

$1$

$4$

$4$

$5$

$6$

$3$

$5$

$$

C$)$ Use the least squares regression method to drive a forecasting equation

D$)$ What are the estimated coal sales if the severity of weather index is $6$ million? Compare the accuracy of the three forecast including moving average using MAD and MSE.

E$)$ Briefly describe six situations in which the first$-$in$,$ first$-$out discipline rule is not applicable in queuing analysis