The rate law is an important concept in chemical kinetics that describes how the rate of a reaction depends on the concentration of the reactants. Each reactant contributes to the overall rate of the reaction, and the rate law is typically determined through experimental data. In this case, the answer '9.0' likely refers to a specific value related to the rate constant or a specific concentration, but without additional context about the reaction or the rate law, we cannot fully interpret its significance. The key takeaway is that the rate law incorporates the concentrations of all reactants, and their individual contributions can vary depending on the reaction mechanism.