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. And so b prime of 5 is going to be equal to 3 times 5 squared minus 12 times 5, which is equal to 75 minus 60, which is equal to 15. And the units here, this is acceleration, so this is going to be, his velocity was in meters per minute, and so this is going to be meters per minute per minute, because remember, time is in terms of minutes. So we could write as meters, let me write it out, meters per minute per minute, which is the same thing as meters per minute, meters per minute squared. Alright, let's do the next part. Based on the model, based on the model b from part c, find Bob's average velocity during the interval from zero is less than or equal to t, is less than or equal to 10. And if the notion of average velocity or average value of a function is completely foreign to you, I encourage you to watch the videos on Khan Academy on finding the average of a function.