Ethylene epoxide (C2H4O) decomposes to form CH4 and CO. Small quantities of H2 and C3H6O are also formed. The following reaction mechanism has been proposed:

1) C2H4O -> C2H3O + H k1

2) H + H + C2H4O -> H2 + C2H4O k2

3) C2H3O -> CH3 + CO k3

4) CH3 + C2H3O -> C3H6O k4

5) CH3 + C2H4O -> C2H3O + CH4 k5

Determine an expression for the rate of decomposition in terms of elementary reaction rate constants and reactant and product concentrations. What is the reaction order with respect to ethylene epoxide?