An experimental serum was injected into 500 guinea pigs. Initially, 150 of the guinea pigs had circular cells, 250 had elliptical cells, and 100 had irregularly shaped cells. After the serum was injected, none of the guinea pigs with circular cells were affected, 50 with elliptical cells were affected, and all those with irregular cells were affected. Determine the empirical probability that a guinea pig with 

(a) Circular cells.

(b) Elliptical cells. 

(c) Irregular cells will be affected by injection of the serum.