We're now going to tackle part B of the potato problem. And it says use the second derivative of eight with respect to time to determine whether your answer in part A is an underestimate or an overestimate of the internal temperature of the potato at time t is equal to three. So in part A, we found the equation of the tangent line at time equals zero, and we used that to estimate what our internal temperature would be at time is equal to three. So how is the second derivative going to help us think whether that was an overestimate or an underestimate? Well, the second derivative can help us know about concavity. It'll let us know, well, is our slope increasing over this interval, or is our slope decreasing? And then we can use that to estimate whether we overestimated or not.