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. We know that this is 1,400 tons of solid waste. This is how much waste there is at time zero, minus 300. So this right over here is 1,400.