We're extrapolating forward from that first point and the current slope. So we really just have to figure out the slope of this line and just see where that line is at T is equal to 1 4th. And you say, wait, how do we know, how do we know what the derivative of W is at zero without knowing W? And that's where we can go straight to this differential equation. We can actually rewrite this differential equation using slightly different notation. This is the derivative of W with respect to T. We could write that as W prime of T is equal to one over 25, one over 25, times the function W, which is a function of T, minus 300. And when you look at it this way, it becomes a little bit clearer on how to figure out what the derivative of W is at zero.