The gates of an amusement park are closely monitored to determine whether the number of people in the amusement park ever poses a safety hazard. On a certain day, the rate at which people enter amusement park is modeled by the function e(x)=0.03x^3+2, where the rate is measured in hundreds of people per hour since the gates opened. The rate at which people leave the amusement park is modeled by the function l(x)=0.5x+1, where the rate is measured in hundreds of people per hour since the gates opened. What does (e−l)(4) mean in this situation?