If you multiply it times some change in time, even infinitesimally small change in time, so d t, this is the amount that flows in over that very small change in time. And so what we want to do is we want to sum up these very small, these amounts over very small changes in time to go from time is equal to 0 all the way to time is equal to 8. So this expression right over here, this is going to give us how many cubic feet of water flow into the pipe. Once again, what am I doing? r of t times d of t, this is how much flows, what volume flows in over a very small interval d t, and then we're going to sum it up from t equals 0 to t equals 8. That's the power of the definite integral, and so this is going to be equal to the integral from 0 to 8 of 20 sine of t squared over 35 d t. And lucky for us, we can use calculators in this section of the AP exam, so let's bring out a graphing calculator where we can evaluate definite integrals. And so let's see, we want to do definite integrals so that I can click math right over here, move down.