A computer retail store sells two types of flat screen monitors: $17$ inches and $19$

inches, with a profit contribution of $$300$ and $$250,$ respectively. The monitors are

ordered each week from an outside supplier. As an added feature, the retail store

installs on each monitor a privacy filter that narrows the viewing angle so that only

persons sitting directly in front of the monitor are able to see on$-$screen data. Each

$17"$ monitor consumes about $30$ minutes of installation time, while each $19"$ monitor

requires about $10$ minutes of installation time. The retail store has approximately $40$

hours of labor time available each week. The total combined demand for both

monitors is at least $40$ monitors each week. How many units of each monitor should

the retail store order each week to maximize its weekly profits and meet its weekly

demand? Formulate a linear programming model