In a particular state, all automobile license plates consist of two capital letters (from A,B,C,...,Z), followed by four digits (from 0,1,2,...9). How many different such license plates are possible:...

Please show all work for A.and B.

Extracted text: In a particular state, all automobile license plates consist of two capital letters (from A,B,C,...,Z), followed by four digits (from 0,1,2,...9). How many different such license plates are possible: **** a) if repetition of letters and digits is allowed. b) if repetition of letters and digits is not allowed.