4. (2 points) A computer password is to consist of 4 alphanumeric characters (an alphanu- meric character is an uppercase letter from A to Z or a digit from 0 to 9). How many such passwords are there if the letter and the digit 0 are excluded to avoid confusion, and if adjacent characters must be different? Answer: 5. (2 points) Three departments have 12, 15, and 18 members, respectively. If each department selects a delegate and an alternate to represent the department at a con- ference, how many ways can this be done