A shop is open 9 AM 7 PM The function rt graphed above give

A shop is open 9 AM - 7 PM. The function r(t), graphed above, gives the rate at which customers arrive (in people/hour) at time t, where t measures time in hours since 9 AM. Suppose that the salespeople can serve customers at a rate of 85 people per hour. Answer the following questions:
A. At what time will people begin having to wait in line before getting served (because the volume of people arriving has become too great)?
B. When is the line longest?
C. How many people are in the line at the time when it\'s the longest?
D. When does the line vanish?