We know that the volume of a rectangular prism is given by:
V = A ยท h
where:
A = surface area
h = height
Therefore, you can solve for A:
A = V / h
= 64 / h
Now, you need to ask yourself by how many numbers you can divide 64. The possible heights are 64, 32, 16, 8, 4, 2 and 1.
Hence:
A) there are 7 possible surface areas (one for each possible height).
B) the maximum Area will be that of the box with the minimum height:
A = 64 / 1 = 64
C) the minimum Area will be that of the box with the maximum height:
A = 64 / 64 = 1