An experimental serum was injected into 500 guinea pigs. Initially, 50 of the guinea pigs had circular cells, 100 had elliptical cells, and 350 had irregular cells. After the serum was injected, all of the guinea pigs with circular cells were affected, 75 with elliptical cells were affected, and none of those with irregular cells were affected. Determine the empirical probability that a guinea pig with (a) circular cells, (b) elliptical cells, and (c) irregular cells will be affected by injection of serum.