Find the volume beneath z=f(x, y) and above the region described by the rectangle with vertices (0, 0), (2, 0), (2, 3), and (0, 3):
J(xy) = x - y + e^(sec-9)
Hint: Compute the double integral required to find the volume under f(x, y) using the limits of integration given by the region on the x-y plane.