What is the rate of change of velocity with respect to time? That's acceleration. So we really just want to evaluate. This Bob's acceleration at t equals 5, that's going to be b prime of 5. So let's first figure out what b prime of t is. b prime of t is equal to, we'll take the derivative here, it's pretty straightforward, just use the power rule. So it's going to be 3t squared minus 12t, 2 times negative 6 is 12, or negative 12, and then the derivative of 300, 300 doesn't change with respect to time, so it's just a zero.