In a sand casting operation, the total liquid hed is maintained constant such that it is equal to the mould height. The time taken to fill the mold with a top gate is tA. If the same mold is filed with a bottom gate, then the time taken in tB. ignore the time required to fill runner and frictional effects. Assume atmospheric pressure at the top molten metal surfaces. The relation between the tA and tB is
(a) High speed steel
(b) Hypo-eutectoid steel
(c) Hyper eutectoid steel
(d) Cast irons