So the rate law of the above elementary chemical reaction is usually described by using the rate law and the rate will depends on the rate constant k and usually depends on the concentration of the reactants. So in this lecture we're only going to look at elementary reactions. But you have to remember that if we're dealing with a multistep complicated reaction, then we cannot simply use the coefficients. In that case, we have to determine the rate law experimentally. But if we have a single step reaction, then we can use the coefficients to calculate the rate law. So in this particular case, going from A to B, a is the reactant and B is the product.