Ok lets do this like this: <span>Let x = length
Let y = width
From this we know that area A=xy. </span><span>Now, perimeter is P=2x+2y
cost would be 3(2x)+2(2y) or 6x +4y=$6,000.00.
From this cost equation we solve for x in terms of y
6x=6000-4y
x=1000-(4y)/6. </span>now lets substitute this value in the area equation A=xy.
A=(1000-4y/6)y
<span>A=1000y−4<span>y2</span>/6=1000y−2<span>y2</span>/3</span>
differentiate and set to equal zero (0)
<span>1000−(−4y/3)=0</span><span>
Solve for y and obtain y=750ft</span>
