$$4NH_3(g) + 5O_2(g) \longrightarrow 4NO(g) + 6H_2O(l)$$
$$2NO(g) + O_2(g) \longrightarrow 2NO_2(g)$$
$$2NO_2(g) + H_2O(l) \longrightarrow HNO_3(aq) + HNO_2(aq)$$
Consider the reactions of the Ostwald process for the production of nitric acid above. The first two reactions have 50% yields and the last reaction has 25% yield.
What mass of $NH_3$ would be needed to produce 126 g of $HNO_3$?