An oil platform which is 9:3 km offshore is connected by a pipeline to a refinery on shore. The refinery is 100 km down the coast from the platform. Oil Platform 913 km c km "' km Refinery 100km The length of the underwater pipe is x km and the length of the pipeline on land is y km. It costs $2 million to lay each km of the pipeline underwater and E1 million per km on land. (a) Show that the cost of the pipeline in millions is C(x) = 2x + 100 - Vx2 - 243 (b) Show that x = 18 gives a minimum cost for this pipeline. Hence find the total length of this pipeline and the minimum cost