The number, in millions, of cars on the road worldwide in the year can be modeled by . In what year does the model predict that there would be 1.4 billion cars worldwide?
When caffeine is metabolized by our body (that is, when our body breaks down, uses, and absorbs caffeine), the decreasing quantity of caffeine can be modelled by the following function , where is the number of hours after an intake of . What is the half-life of caffeine in our body (that is, how long does it take for our body to break down half of the caffeine)? Round your answer to the nearest hour.