$[6]$ Please carefully read the following scenario:

A publishing house publishes three weekly magazines$-$Daily Life, Agriculture Today, and Suf's Up$.$ Publication of one issue of each of the magazines requires the following amounts of production time and paper:

$\backslash$table$[[,$Production $($hr$),$Paper $($lb$.)],[$Deily Life,$0\mathrm{.}01,0\mathrm{.}2],[$Agricuture Today,$0\mathrm{.}03,0\mathrm{.}5],[$Surf$\text{'}$s Up$,0\mathrm{.}02,0\mathrm{.}3]]$

Each week the publisher has available $120$ hours of production time and $3,000$ pounds of paper. Total circulation for all three magarines must exceed $5,000$ issues per week if the company is to keep its advertisers. The selling price per issue is $$2\mathrm{.}25$ for Daily Life, $$4\mathrm{.}00$ for Agrictithre Today: and $$1\mathrm{.}50$ for Sur's Up$.$ Based on past sales, the publisher knows that the maximum weekly demand for Daily Life is $3,000$ issues; for Agriciture Today, $2,000$ issues; and for Surf's $U_{p,},6,000$ issues. The production manager wants to know the number of issues of each magazine to produce weekly in order to maximize total sales revenue.

The total number of decision variables in this problem is:

$4$

$2$

$5$

$3$