The Evan's family has a backyard that is in the shape of a rectangle. One side is 48 ft and the other side is 50 ft. They are doing some construction. The Evan's family will build a flower bed in the center of the yard. It will be a square with sides measuring 14ft. After the flower bed is dug up they will place grass in the remaining area. How much grass should the Evan's purhcase?