Quasi Steady State

For the mechanism proposed below, use the quasi (pseudo) steady state approximation to determine the overall rate law assuming the pseudo steady state.
$$2~NO~+~2 H_2~\longrightarrow~2~H_2O~+~N_2~~{overall}$$$$2~NO+~H_2~\mathop{\leftrightharpoons}^{k_1}_{k_{-1}}~N_2O~+~H_2O$$ $$N_2O~+~H_2~\xrightarrow{k_2}~N_2~+~H_2O$$