Answer:
c. all accounts fewer than 31 or more than 60 days past due.
Step-by-step explanation:
The Universal Set is the set of all past due accounts.
Event A = the event that the account is between 31 and 60 days past due.
Event B = the event that the account is that of a new customer.
Therefore, the complement of A will be the event of all the accounts fewer than 31 or more than 60 days past due.
The correct option is C.