You have been asked to create four-character password for your computer using:

the 26 upper case letters of the alphabet (A, B, C, ...)

the 26 lower case letters of the alphabet (a, b, c, ...)

the digits from 0 to 9

the symbols: ~ ! @ # $ % ^ & *

a) How many different four-character passwords are possible if any of the letters, digits, or symbols can be used for each character if repetition is not allowed? Show your work.

b) How many four-character passwords begin with a letter and end with a digit if repetition is allowed? Show your work.

c) How many different four-character passwords containing at least one symbol are possible if repetition is allowed? Show your work.