Pick the WRONG design guideline for a reactor in which the reactions, A → R (desired) and A → S (undesired) are to take place. The ratio of the reaction rates is $$\frac{{{{\text{r}}_{\text{R}}}}}{{{{\text{r}}_{\text{S}}}}} = \frac{{{{\text{k}}_1}}}{{{{\text{k}}_2}}} \cdot {{\text{C}}_{\text{A}}}^{{\text{a}} - {\text{b}}}$$