What is the lateral area of the drawing

Here we have a base of 5mi*5mi and a height of 2 mi.

If we want to calculate the lateral area, we only need to calculate the area of the 4 lateral sides (the lateral sides are all of those that aren't the bottom of the top)

we know that the area of a rectangle is the product of its sides, then, in this case, each of the lateral rectangles has an area of 5mi*2mi = 10mi^2.

and we have 4 lateral sides  

then the area of the lateral sides is 4*10mi^2 = 40mi^2

then the correct answer is C.