Use the grid averaging $($cross$-$section$)$ method to estimate the quantity of cut and$/$or fill required for a ${25}^{\text{'}}{25}^{\text{'}}$ grid with

existing elevations of ${69\mathrm{.}50}^{\text{'}},{70\mathrm{.}80}^{\text{'}},{71\mathrm{.}20}^{\text{'}},$ and ${72\mathrm{.}10}^{\text{'}}$ at its four corners. Assume the proposed rough grade level to be

${72\mathrm{.}60}^{\text{'}}$ at all four corners.