Plot the monthly sales data.

Forecast January sales using each of the following:

Naive method.

A $3-$month moving average.

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

Exponential smoothing using an

and a September forecast of $18.$

A trend projection.

With the data given, which method would allow you to forecast next March$$s sales? $($MyLab Operations Management also includes a shorter $($brief$)$ version of this problem.$)\backslash$table$[[$MONTH$,$SALES$],[$January$,20],[$February$,21],[$March$,15],[$April$,14],[$May$,13],[$June$,16],[$July$,17],[$August$,18],[$September$,20],[$October$,20]]$