Introduction to optimization

In a small town near a lake, customers are willing to pay between $\$50$ and $\$200$ for renting a boat for the day. The owners of a boat rental company have figured out that the number of boats $N$ that they rent per day can be modeled by the linear function $N(x) = 200 - x$, where $x$ is the price of renting a boat. If they charge $\$50$ per day or less, they will rent all their boats. If they charge $\$200$ per day or more, not a single boat will be rented. How much should the owners of the rental company charge to maximize their revenue?