The market price of cheeseburgers in a college town increased recently, and the students in an economics class are debating the cause of the price increase. Some students suggest that the price increased because several burger joints in the area have recently gone out of business. Other students attribute the increase in the price of cheeseburgers to a recent increase in college student enrollment. The first group of students thinks the increase in the price of cheeseburgers is due to the fact that several burger joints in the area have recently gone out of business.