Calculus problem; Need help in expressing it!

The rate at which people enter an amusement park on a given day is modeled by the function E defined by E(t)= 15600/(t^2-24t+160)

E(t) is measured in people per hour and time t is measured in hours after midnight. The function is valid for 10 ≤ t ≤ 20, the hours during which the park is open today. At t=10 there are no people in the park. During what hour is the rate at which people are entering the amusement park the greatest? (Think maximum!)

.... why you specify today? It's a bit confusing.
The function is valid for t ranging 10 ≤ t ≤ 20 where t represents the hours that park is opened.


Which hour of the day that records the highest rate of people entering the amusement park?


... Is this a part of the sum? It's not very clear.