∴SABCD=AB？ AD=x(20-23x)(？ 4? Integral)
The warehouse area is not less than 144 square meters.
∴x(20-23x)≥ 144
∴ 12≤x≤ 18(？ 6 points)
(2) From the meaning of the question, V storage capacity = x2 (20? 23x)=9？ 13x？ 13x(20？ 23x)≤9？ ( 13x+ 13x+20？ 2x33)3=80003，
If and only if 13x = 20? 2x3, that is, when x=20 (m), the maximum V is 80003 (m3) (12 minutes).