(a) By applying the relevant knowledge, the Total Solidification Times(TST) of three casting shapes are to be calculated and compared: (1) a sphere with diameter 1⁄4 10 cm, (2) a cylinder with diameter and length both 1⁄4 10 cm, and (3) a cube with each side1⁄410 cm. The same casting alloy is used in the three cases. Determine the relative solidification times for each geometry. If the mold constant 1⁄4 3.5 min/cm2 in Chvorinov's rule, compute the total solidification time for each casting. (b) Based on the results of part (a), which geometric element would make the best riser and why? Present an analysis-based comment on the outcome.