$\backslash$table$[[$MONTH$,$SALES$],[$January$,20],[$February$,21],[$March$,15],[$April$,14],[$May$,13],[$June$,16],[$July$,17],[$August$,18],[$September$,20],[$October$,20],[$November$,21],[$December$,23]]$

a$)$ Plot the monthly sales data.

b$)$ Forecast January sales using each of the following:

i$)$ Naive method.

ii$)$ A $3-$month moving average.

iii$)$ A $6-$month weighted average using $.1,\mathrm{.}1,\mathrm{.}1,\mathrm{.}2,\mathrm{.}2,$ and $.3.$ with the heaviest weights applied to the most recent months.

iv$)$ Exponential smoothing using an $=\mathrm{.}3$ and a September forecast of $18.$

v$)$ A trend projection.

c$)$ With the data given, which method would allow you to forecast next March's sales? PX $($MyLab Operations Management also includes a shorter $($brief$)$ version of this problem.$)$