OK, to do this problem, think about S equaling 9 T to the -2 -, 3 T to the -1. So the velocity -18 T to the -3 + 3 T to the -2. The acceleration would be +54 T to the -4 -, 6 T to the -3. Now we try not to leave negative exponents. So -18 / t ^3 + 3 / t ^2 acceleration's going to be 54 / t to the 4th -6 / t ^3. So now if we want to do the end points, we just put the body's displacement. We're going to say what's S of 3 -, s of one, and we're going to compute that the average velocity is going to be that S of 3 -, s of 1 / 3 - 1. The body's speed is the absolute value of V of three and the absolute value of V of one. The body's acceleration a of three and a of one, and the interval of does the body ever change direction? So we're going to set the velocity equaling to zero and we're going to solve and when we do this, we're going to realize if we multiply everything through by AT cubed, we'd get 0 equaling -18 + 3 T or T is going to equal 6. But six isn't within the interval one to three. So there is no change direction during the specified interval.