The following rectangular pyramid has a height of 2 units and a volume of 18 cubic units. The oblique rectangular prism has a congruent base and the same height, and its slant height is 3 units.

What is the volume of the prism?
(Choice A)
A
6 cubic units

(Choice B)
B
18 cubic units

(Choice C)
C
36 cubic units

(Choice D)
D
54 cubic units