Give the step-by-step reasoning process and then the final answer. Tiffany is going to the beach and wants to make sure she has enough sunscreen. She knows she needs to re-apply sunscreen after 2 hours. She also knows she needs 3 ounces of sunscreen each application and a bottle contain 12 ounces and costs $3.5. If she is there for 16 hours, how much will the sunscreen cost?
She needs to apply sunscreen 8 times because 16 / 2 = 8. She will use 24 ounces of sunscreen because 3 x 8 = 24. This will take 2 bottles because 24 / 12 = 2. This will cost $7 because 2 x 3.5 = 7.
The final answer: 7.