License plates in a particular state are to consist of 2 digits followed by 3 uppercase letters. ​a) How many different license plates can there be in this state if repetition of letters and numbers is​ permitted? ​b) How many different license plates can there be in this state if repetition of letters and numbers is not​ permitted? ​c) How many different license plates can there be in this state if the must be ​, and repetition of letters and numbers is not​ permitted? ​d) How many different license plates can there be in this state if the first digit cannot be ​, and repetition of letters and numbers is not​ permitted?