Mean Absolute Deviation $($MAD$)$

Calculate the Mean Absolute Deviation $($MAD$)$ using the following data.

$($Refer to Slides $52,53,$ and $54$ in Chapter $02-$or$-$Pages $54$ and $55$ in the textbook$)$

$\backslash$table$[[$Month$,\backslash$table$[[$Actual$],[$Sales$]],$Forecast$],[$JAN$,\frac{?}{\text{b}\text{a}\text{r}}(1,345),1,340],[$FEB$,1,445,1,435],[$MAR$,1,470,1,460],[$APR$,1,390,1,490],[$MAY$,1,340,1,370],[$JUN$,1,345,1,350],[$JUL$,1,300,1,295],[$AUG$,1,375,1,375],[$SEP$,2,152,2,144],[$OCT$,2,312,2,296],[$NOV$,2,352,2,336],[$DEC$,2,224,2,379]]$