And so we're going to begin by making the following assumption. So when the time is approximately equal to zero at the beginning of that chemical reaction, the Km value is much greater than the concentration of that substrate. And so what that means is this sum, the Km value plus the substrate concentration is simply approximately equal to the Km value because this is much greater than this. This is approximately equal to zero compared to this. And so Km is approximately Km plus the subsequent is approximately equal to Km. So this is approximately equal to zero.