Consider a reaction A+R arrow Product. The rate of this reaction is...

Consider a reaction $A+R \rightarrow$ Product. The rate of this reaction is measured to be $k[A][R]$. At the start of the reaction, the concentration of $R,[R]_0$, is 10 -times the concentration of $A,[A]_0$. The reaction can be considered to be a pseudo first order reaction with assumption that $k[R]=k^{\prime}$ is constant. Due to this assumption, the relative error (in \%) in the rate when this reaction is $40 \%$ complete, is _______ [ $k$ and $k^{\prime}$ represent corresponding rate constants]