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The diagram below represents the cross-section of a bridge with a solid part and a tunnel through which the river flows. The tunnel is 8 m long and its cross-section is a semi-circle of radius is 3.5m. The bridge is 5m high and its solid part is filled with concrete.
(a) Calculate
(i) The cross-sectional area of the solid part.
(ii) The volume of concrete used to fill the solid part.
(b) Concrete is made by mixing gravel, sand
and cement in the ratio 5:4:1 by mass. Given that the density of concrete is 1.8g/#cm^3# and that one bag of cement has a mass of 50kg, calculate the number of bags of cement used in constructing the bridge.