Counting Principles

Question #1 A door lock code consists of four letters followed by four digits. Only upper case letters A to E and numbers 1 to 6 can be used. If letters and numbers cannot be repeated, how many different door codes are possible? Question #2 A teacher wants to give an eight-question quiz with questions she can pull from a pool of 30 questions. How many quizzes, with different questions, can she make from the pool of 30 questions? Question #3 In a 5K race to support cancer research, prizes are given to first- through fourth-place finishers. If 75 people run the race, how many possible ways can first through fourth place be rewarded?