As a young entrepreneur, Jon has a goal to earn enough money to start his own business. His goal is to earn $1,500 of profit each summer until he graduates from high school. After some practice, he has developed some skill in mowing lawns. He purchased his lawn mower, weed eater and a broom for a total of $400. With gas and expendables, his variable cost per lawn is $15. After doing market research, he intends to charge $40 per lawn.

 How many lawns would he have to mow in order to make is goal of $1,500?