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. We literally, the slope of this line, the slope of that line literally is just the derivative of W evaluated at zero. So let's literally take the derivative of W and evaluate it at zero. So we have W prime of zero is equal to one over 25 times W of zero, which we know.