Nitric acid whose worldwide annual production is nearly 10

Question

Nitric acid, whose worldwide annual production is nearly 10 billion kilograms, is used to make many products, including fertilizers, dyes and explosives. The first step in the process is the oxidation of ammonia:

4NH₃(g) + 5O₂(g) ---> 4NO(g) + 6H₂O(g)

Calculate the enthalpy of the reaction (Δ H^orxn) using the molar enthalpy of formation values (ΔHfo).