Please solve

2. (15 points) Let a be the last digit of your student ID, and you have to set up the password for a computer system. The general rules for password setting are: The password length, i.e., number of characters in a password, is between ((a mod 4) +3) and ((a mod 4) + 5). ii. Each character in the password is a lowercase letter or a digit. ii. Each password must contain at least one digit. Based on the above password setting policy, a) (12 points) How many possible passwords are there? b) (3 points) Suppose someone is using brute-force attack to decode your password, i.e., try every possible password until he/she can successfully log into your computer. To better protect your computer system, which password length would you prefer, ((a mod 4) + 3), (Ca mod 4) + 4)or (Ca mod 4)+ 5)? Briefly explain why