Answer
$\text{Rate} = k[H_2O_2][I^{-}]$
Work Step by Step
The rate-determining step is always the slowest step. To determine the exponents of the rate law, look at the number of moles of each reactant in the slowest step. In this case, there is 1 mole of $H_{2}O_{2}$ and 1 mole of $I^{-}$ in the reactants of the slow step.
