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. And so we have W prime at time equals zero. So our slope at time equals zero, our derivative at time equals zero, is equal to one over 25 times 1,400 minus 300 is 1,100. Minus 300 is 1,100.