Passwords consist of 7 symbols which can be of three types, i. e. uppercaseletters, special symbols or digits. Assume that there are 32 letters, 20 special symbols and 10 digits. Assume that all such passwords are valid (e.g AASY3B4, BASY3B4 and ####%%%) a) How many passwords contain only one type of symbols (for example only special symbols)? Show a formula but you do not have to compute a final answer. b) Let us require that a password must have a special symbol in the last position or in the second last position. How many passwords fulfill thos condition? Show a formula but you do not have to compute a final answer. Show arguments.