Each pen would have 1200 ÷ 4 = 300 m of fence, so 2L + 2W = 300 reduced L + W = 150, so L = 150 -W

Area, A, equals L XW, substitute 150 - W for L So A = 150 - W x W given you a quadratic function

-W^{2 }+ 150W, use x = -b/2a to get x coordinate of vertex (h,k) [maximum]

-150/2(-1) = 75 = max W so L = 150 - 75 = 75

max area of 1 pen = 75 x 75 = 5,625 m^{2}

max area of all 4 pens = 4 x 5625 = 22,500 m^{2}