Xy=72, and the minimum value of S=(x+2)(y+4) is required.

s = xy+8+4x+2y = 80+4x+ 144/x & gt； Under the root sign = 80+2 (4x *144/x) =128 (using average inequality).

Then the minimum area of the road is 128-72 = 56 (DM 2).