Now ready for part B, and I've wiped all the salt off of my fingers, and I've had a glass of water, so now I'm ready for some business. Find the second derivative of W with respect to T. In terms of W, use this second derivative to determine whether your answer in part A is an underestimate or an overestimate for the amount of solid waste that the landfill contains at time T equals 1 fourth. So let's do the first things first. Let's find the second derivative in terms of W. And we already have the first derivative over here, and in part A I rewrote it just with slightly different notation, but I'll just use this just because I need to write down here and I can still refer to this thing. So let's just take the derivative of both sides of this differential equation with respect to T. So you take the derivative of this left-hand side with respect to T, you get the second derivative of W with respect to T as a function of T is equal to, and you take the derivative of this with respect to T, this is the same thing as 1 over 25 WT minus 12. And so when you take the derivative, that constant part drops off and you're just left with 1 over 25 times the derivative of WT. And let me make that clear.