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). Assume all paswords are equally likely. Let A and B denote the events that consist of passwords with only letters or only integers, respectively. Determine the follwing probabilities:
(a). P(AUB)
(b). P(A{}'\cup B)=
(c). P(Password contains exactly 1 or 2 integers)=