Problem 1 - Monthly Billing
Problem 2 - Test Monthly Billing
Problem 3 - Correct return_account_balance
Problem 4 - Comment code
Problem 5 - commit new policy
Problem 6 - add insured to policy
Problem 7 - non-pay notice check
Problem 8 - change payment plans
Problem 9 - add Cancel Policy method
Problem 10 - browser interface
Bonus - DRY make_invoices