ratio of solidification time of a sphere to that of a cylinder of equal volumes

Question

In a sand casting process, a sphere and a cylinder of equal volumes are separately cast from the same molten metal under identical conditions. The height and diameter of the cylinder are equal. The ratio of the solidification time of the sphere to that of the cylinder is

(a) 1.14                   (b) 0.87

(c) 1.31                   (d) 0.76