Two $S_{\text{N}}2$ experiments with the same haloalkane and nucleophile differ only in concentration. Run A uses $0.70\ \text{mol/L}$ of haloalkane and $0.18\ \text{mol/L}$ of nucleophile. Run B uses $0.35\ \text{mol/L}$ of haloalkane and $0.36\ \text{mol/L}$ of nucleophile. What is the ratio of the rate in run B to the rate in run A?