Please help me using c++ to solve this problem ? Thank you guys so much

7. Passwords on a certain system have exactly 5 letters that are either lowercase letters or uppercase letters. (a) How many possible passwords are there? (b) How many possible passwords are there that use only lowercase letters? (c) How many possible passwords are there that use only uppercase letters? (d) How many possible passwords are there that use at least one uppercase letter and at least one lowercase letter?