Students at a state college may preregister for their fall classes by mail during the summer. Those who do not preregister must register in person in September. The registrar can process 35 students per hour during the September registration period. Suppose that after 4 hours in September, a total of 360 students (including those who preregistered) have been registered.

a. Express the number of students registered as a function of time and draw the graph.

b. How many students were registered after 3 hours?

c. How many students preregistered during the summer?