We can approximate the double integral z 6 0 z 6 0 x + y 3 dy dx with a riemann sum by partitioning the region d = {(x, y)|0 ≤ x ≤ 6, 0 ≤ y ≤ 6} into four equal squares. and if we choose the upper right corner of each square as the sample point, which of the following is the approximated value of the double integral?