Area for a rectangle -> A=WL
[tex]\begin{gathered} A=W\cdot L \\ A=W\cdot(1000-2W) \\ A=1000W-2W^2 \end{gathered}[/tex]Let's derive the equation A
[tex]\begin{gathered} A^{\prime}=1000-4W=0 \\ 4W=1000 \\ W=250ft \end{gathered}[/tex]If W=250, we have
[tex]L=1000-2\cdot250=1000-500=500ft[/tex]Finally, the area
[tex]A=W\cdot L=250\cdot500=125000ft^2[/tex]