Now once again we begin the same way. Negative change in concentration of x over change in time is equal to our constant KDF times the concentration of x to the one power. So now this guy remains. So let's rearrange them a bit and we get well, we bring that change in concentration of x over this side and we bring our time or change in time to this side. We also bring the negative over to this side and we get change in concentration of x divided by concentration of x equals negative our constant times change in time. Now, in order to get from this guy to this guy, we have to use calculus and integrals.