Which relation is a function?

Can someone me with the property questions for 12 13 and 14 plz

At the beginning of year 1, carlos invests $600 at an annual compound interest rate of 4%. he makes no deposits to or withdrawals from the account. which explicit formula can be used to find the account's balance at the beginning of year 5? what is, the balance?

The cost of turkey is directly proportional to its weight. if a 12-pount turkey costs $27, how much does a 13-pound turkey cost? a. $33.75 b. $36.00 c. $31.00 d. $32.50