Three casting of same weight and material are to be produced. Shapes of the three casting are:

cube, sphere and cylinder. Find the cooling time ratio in all these cases $($cube$/$sphere$,$

sphere$/$cylinder$,$ and cube$/$cylinder$).$ Assume the cylindrical shaped casting have length to radius

ratio of $0\mathrm{.}5.$ The top and bottom face of cube, and the top hemisphere surface of sphere are

insulated.