$4.$ A can$-$opener manufacturer has had monthly sales for a seven$-$month period as follows: L$03$ & LO$4$

$*$Plot the data.

Month

February

Sales $(000$ units$)$

$19$

March

$18$

April

$15$

May

$20$

June

$18$

July

$22$

August

$20$

b$.$ Forecast September's sales volume using each of the following:

i$.$ A linear trend equation. $($Use of Excel's Trendline, with Display Equation on Chart option, is recommended.$)$ ii$.$ A four$-$month moving average.

iii. Exponential smoothing with a smoothing constant of $0\mathrm{.}10,$ assuming a March forecast of $19(000).$

iv$.$ The na$$ve approach.

v$.$ A weighted average using $0\mathrm{.}50$ for August, $0\mathrm{.}30$ for July, and $0\mathrm{.}20$ for June.

c$.$ Which method seems least appropriate? Why?

d$.$ What does use of the term sales rather than demand presume?