The volume of a prism can be calculated using the following formula, where B is the area of the base and h is the height.
V=Bh
By the Cavalieri's Principle, the formula still holds true for oblique prisms. We can see from the diagram that the base area of the prism is 11.4ft^2 and its height equals 5.1ft. Let's substitute these values into the formula and solve for V.