In a particular mold design, the down sprue has an area of Cross section of 6.45 cm2 where the pouring basin leads into the sprue. The sprue is 20 cm long. The required metal flow rate at the top section of the sprue is 820 cm3/s. determine the pouring height necessary above the sprue top. Also determine the area of C.S. of the sprue at its bottom to avoid the aspiration of liquid molten metal.