A Shop Is Open from 9am-7pm

Short Answer

A shop is open from 9am-7pm. The function graphed below gives the rate at which customers arrive (in people/hour) at time t. Suppose that the salespeople can serve customers at a rate of 80 people per hour.
A. People have to start waiting in line before being served at about _____ o'clock.
B. The number of people in line when the line is the longest is about _____.