Let V be the volume of the solid that lies under the graph of f(x, y) and above the rectangle given by 0 ≤ x ≤ 2, 2 ≤ y ≤ 6. We use the lines x = 1 and y = 4 to divide R into subrectangles. Let L and U be the Riemann sums computed using lower left corners and upper right corners, respectively. Without calculating the numbers V, L, and U, arrange them in increasing order.
f(x, y) = 40 - x^2 - y^2