( 1)ab=a=50

ad=225/50=4.5

a b+ 2ad = 59 & lt； 60 meters

So it can be enclosed, AB=50 meters.

(2) The length of A has a restrictive effect on the solution, with length +2* width.

(3)

x*(60-x)/2=400

60x-x^2=800

x^2-60x+800=0

(x-20)(x-40)=0

X=20 or x=40

So we can enclose a warehouse with a total area of 400.

When x = 20 and y = 20.

When x = 40 and y = 10.