The surface area of a regular pyramid with a square base which has a slant height of 5 units and base side lengths of 9 units is:

A) 360 units squared

B) 252 units squared.

C) 171 units squared.

D) 117 units squared.

Base area = area of a square = 9^2 = 81 units^2 (1)

Area of the sides = area of 4 trianges each with a base of 9 and height of 5 =

4* (1/2)(9)(5) = 90 units^2 (2)

Surface area = (1) + (2) = [ 81 + 90 ] = 171 units^2