A Social Security number is used to identify each resident of the United States uniquely. The number

Question:

A Social Security number is used to identify each resident of the United States uniquely. The number is of the form xxx–xx–xxxx, where each x is a digit from 0 to 9.
(a) How many Social Security numbers can be formed?
(b) What is the probability of correctly guessing the Social Security number of the president of the United States?