National Scan, Inc sells radio frequency inventory tags. Monthly sales for a seven$-$month period

were as follows:

Month Sales $(000$ units$)$

Feb. $20$

Mar. $19$

Apr. $16$

May $21$

Jun. $19$

Jul. $23$

Aug. $21$

a$.$ Plot the monthly data on a sheet of graph paper.

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

$(1)$ The naive approach

$(2)$ A five month moving average

$(3)$ A weighted average using $\mathrm{.}60$ for August, $\mathrm{.}30$ for July, and $\mathrm{.}10$ for June

$(4)$ Exponential smoothing with a smoothing constant equal to $20,$ assuming a a March $-$forecast of

$19(000)$

$(5)$ A linear trend equation

c$.$ Which method seems least appropriate? Why? $($Hint: Refer to your plot from part a$.)$

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