The question is:

What i have done so far is that i have solved for y where . I have also solved the triangle on top of the rectangle where the . (its x times root 3)A gable window has the form of a rectangle topped by an equilateral triangle, the side of which are equal to the width of the rectangle. Find the maximum area of the window if the perimeter is 600cm.

I am just not sure what to do from there.

Thank you in advance!