Answer
$\int_{0}^{120}r(t)~dt~~$ represents the number of gallons of oil that leaked from the tank in the first 120 minutes.
Work Step by Step
We can state the Net Change Theorem as follows:
The integral of a rate of change is the net change:
$\int_{a}^{b}F'(x)~dx = F(b)- F(a)$
$~~r(t)~~$ is the rate at which oil leaks from a tank measured in gallons per minute.
Therefore, $~~\int_{0}^{120}r(t)~dt~~$ represents the number of gallons of oil that leaked from the tank in the first 120 minutes.