Aziz is building a rectangular planter up against an existing concrete fence. He wants to build the planter with 4-inch wide wood boards. He has 50 of these boards which gives him a total length of 200 inches for the walls of the planter. He wants to maximize the area of the planter so he will also use leftover 8-inch long concrete blocks on each side of the planter that is against the concrete. What is the length and width of the planter that he can make that would give him the maximum area?