Consider a reaction A + R → 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′ is constant. Due to this assumption, the relative error (in %) in the rate when this reaction is 40 % complete, is _____. [k and k′ represent corresponding rate constants]