Total solidification times of three casting geometries are to be compared: (1) a sphere, (2) a cylinder, in which the length-to-diameter ratio = 1.0, and (3) a cube. volume = 1000 cm3 for all three shapes, and the same casting alloy is used. (a) determine the relative solidification times for each geometry. (b) based on the results of part (a), which geometric element would make the best riser? (c) if the mold constant = 3.5 min/cm2 in chvorinov's rule, compute the total solidification time for each casting.