Help me please i can’t figure it out

Which of the following tables represents exponential functions?

Given the equation f(x)=a(b)x where the initial value is 40 and the growth rate is 20% what is f(4)

Part a: sam rented a boat at $225 for 2 days. if he rents the same boat for 5 days, he has to pay a total rent of $480. write an equation in the standard form to represent the total rent (y) that sam has to pay for renting the boat for x days. (4 points)