Which of the following is the point at which no more metal can be fed into the microstructure of a solidifying casting from the riser? O Central Fraction Solid point O Critical Fraction Solid point O Central Fusion Solid point O Central Fraction Liquid point 100% Solid Point Which of the following is an effect of slow casting cooling rates? gas floatation O smaller grains O gas entrapment o fine microstructure less segregation of alloying elements