Please help with explanation!

Find the length L and width W {with W 5 L) of the rectangle with perimeter 4'3 that has maximum area, and then find the maximum area. L=Ci W=C1 Maximum area = [j A fence is to be built to enclose a rectangular area of 280 square feet. The fence along three sides is to be made of material that costs 6 dollars per foot, and the material for the fourth side costs 14 dollars per foot. Find the length _ and width W (with W/