Use the experimental data in this table to determine the rate law for the reaction of hydrogen iodide, HI, with ethyl iodide, ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{I}$.

[HI], M	${\left[{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{I}\right]}_{,}\mathrm{M}$	Rate, $\mathrm{M}.{\mathrm{s}}^{-1}$
0.010	0.010	$1.2\times {10}^{-5}$
0.010	0.020	$2.4\times {10}^{-5}$
0.020	0.030	$7.2\times {10}^{-5}$