A shed in the shape of a rectangular prism measures x feet high, x + 6.5 ft wide, and is x - 4 ft deep. The volume of the shed is given by the function V(x) = x² + 2.5x - 26.
a) x² + 2.5x - 26
b) x² + 2.5x - 22.5
c) x² + 2.5x - 21.5
d) x² + 2.5x - 20