15) What is the minimum number of cross-sections required to find the quantity of earth work using trapezoidal formula?

16) What minimum number of cross-sections required for applying prismoidal formula in volume calculations?

17) What is the nature of earth work if the G.L.218 and F.L.220?

18) What is the nature of earth work if the G.L.300 and F.L.280?

19) What is the nature of the earth work if the ground level is less than the formation level?