A computer password consists of seven characters.(a) How many different passwords are possible if each character may be anylowercase letter or digit?(b) How many different passwords are possible if each character may be anylowercase letter or digit, and at least one character must be a digit?(c) A computer system requires that passwords contain at least one digit. Ifseven characters are generated at random, and each is equally likely to be any ofthe 26 letters or 10 digits, what is the probability that a valid password will begenerated?