The materials used in construction is pertaining to the total volume on the porch.

\(V = V_1 + 6V_2\), where \(V, V_1 ~ and ~ V_2\) is the total volume, volume of \(6'x7'\) area and volume of one rectangular parallelepiped step respectively.

\(V_1 = lxwxh = 6x7x\frac{7}{3} = 98\), \(h = \frac{7x4}{12} = \frac{7}{3}'\)

\(V_2 = \frac{11x7}{144} (7)\), convert 11 and 7 inches to ft.

\(V_2 = \frac{539}{144}\)

\(V = 98 + (6) (\frac{539}{144})\)

\(V = 120.46 ~ft^3\) Answer