Stores A, B, and C, have 50, 75, and 100 employees and respectively 50%, 60%, and 70% if these employees are women. Resignations are equally likely among all employees regardless of sex. One employee resigns and she is a woman. What is the probability that she works in Store C?

Suppose E and F are mutually exclusive events of an experiment. Show that if independent trials are performed of this experiment, the E will occur before F with the probability P(E) / (P(E)+ P(F)).