2. 10 buildings to be inspected today and there are 10 inspectors. How many different ways could the buildings and inspectors be paired up? 3. A certain type of engineering license number is made up of 6 characters: the first 3 are numbers, while the nal 3 are letters. (i) How many different license numbers can be made if repetition of the characters are allowed? (ii) How many different license numbers can be made if repetition of the characters are not allowed