People enter a line for an escalator at a rate modeled by the function r given by r(1 ) = 44 100 for 0 S t S 300 300 0 for t > 300, where r(1) is measured in people per second and t is measured in seconds. As people get on the escalator, they exit the line at a constant rate of 0.7 person per second. There are 20 people in line at time t = 0. (a) How many people enter the line for the escalator during the time interval 0 S : $ 300 ? (b) During the time interval 0 S :