Oliver has a savings account that pays 4% monthly interest. He made an initial deposit of $50 and plans to leave the money in the account for 35 months without making any other deposits or withdrawals.

Over the same period of time, Oliver will use the funds in a checking account to pay his $15 monthly membership fee at the gym. He begins with $450 in that account and does not make any other deposits or withdrawals.

The graph below represents the functions that model the changes in Oliver's account balances.