You work for a rental car company. If customers return a car with under half a tank of gas, they are charged $8 per gallon of gas to fill up the tank. Otherwise, it costs $4 per gallon of gas to fill up the tank. A customer returns a rental car that has a tank capacity of 16 gallons. If the rental car is returned with 800 fluid ounces of gasoline in it, how much should you charge the customer to fill the tank?
A.$14
B.$28
C.$39
D.$78