A bag contain 'a' white balls and 'b' black balls. We follow the following Steps:

(1) A bag in chosen at random and is discarded.

(2) A Second ball is chosen, If its color is different from the previous ball then it is replaced in the bag and the process is repeated from the begining.

if its color is the same it is discarded and we start from step(2).

Find the probability that the last ball in the bag is White