Mechanism of Catalytic Reaction: Adsorption Calculations

Problem:
Develop the overall rate equation for the gas-phase heterogeneous reaction A --> M + N, considering the following steps:
i. adsorption of A,
ii. surface reaction between the adsorbed A and adjacent site to produce adsorbed M and adsorbed N, and
iii. desorption of M and N
Assume step (ii) is controlling.