A function f gives the rate of change of a quantity Q (in units per hour) with respect to time t (in hours). Which of the following expressions represents the net change in Q from t=2 to t=7?
a) ∫27∣f(t)∣dt
b) ∫27f(t)dt
c) 5(f(7)−f(2))
d) 51∫27f(t)dt