Find the surface area of a rectangular prism having dimension 3 feet x 4 feet x 5 feet?

Check the picture below

so the prism is really 6 rectangles stacked up to each other at the edes, so we can simply get the area of all 6 and sum them up, to get the area of the rectangular prism.

0.02040816326

if x = 1, then the answer is 3.5