AB=X and then ad = 60-X.

D: X(60-X)=400

D: X= 30+/- 10 root number 5

X = 7.64 or x2= 52.36

2. When x = -b/2a = 30, there is a maximum value =30*960-30)=900.

Therefore, when AB=30M, the maximum area is 900m2.