1. a computer system uses passwords that contain exactly eight characters, and each character is one of the 26 lowercase letters (a-z), or 26 uppercase letters (a-z) or 10 integers (0-9). let ω denote the set of all possible passwords, and let a and b denote the events that consist of passwords with only letters or only integers, respectively. suppose that all passwords in ω are equally likely. determine the following probabilities: (a) p(a|b′) (b) p(a′ ∩b)