Let the base be a and the height be h, then the volume v = a 2 * h = 256.

So h = 256/a 2 ....................... (1)

The required materials are: S = 4ah+A2 ...................... (2).

Bring (1) into (2)

S=4a 256/a^2+a^2

=a^2+256*4/a

Derived from the above formula:

S'=2a-256*4/a^2………………………………(3)

When S'=0, that is, formula (3) is 0, the maximum value of s can be obtained.

That is, when a=8, the minimum value of s is 192.