so hmmm, notice the picture below
the perimeter is just w + w + l or 2w+l
thus [tex]\bf \textit{area of a rectangle}\\\\
A=lw\qquad 4800-2w=l\implies A(w)=(4800-2w)w
\\\\\\
A(w)=4800w-2w^2[/tex]
take the derivative of A(w), then zero it out to get the critical points, and do a first-derivative test on the critical points for any maxima between 0 and 4800
