For zero is less than or equal to t is less than or equal to 10, Bob's velocity is modeled by b of t is equal to t to the third minus 60 squared plus 300, where t is measured in minutes and b of t is measured in meters per minute. Find Bob's acceleration at time t equals 5. Well, acceleration, this is a velocity function right over here, so the acceleration is going to be the derivative of the velocity function with respect to time. 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.