$16.$ The field data below are the result of a survey to determine the original ground elevation for a road project. If the new road will be at an excavated elevation of $840\mathrm{.}55$ ft and will have $38$ ft road base width, calculate the volume between stations $\backslash (5+00\backslash )$ and $\backslash (6+50\backslash ),$ using:

a$.$ The end area formula

b$.$ The prismoidal formula