Relation between equilibrium constants of combined reactions

2017 1 question

1. The equilibrium constants of the following are: $N_2 + 3H_2 \rightleftharpoons 2NH_3$, $K_1$; $N_2 + O_2 \rightleftharpoons 2NO$, $K_2$; $H_2 + \frac{1}{2}O_2 \rightarrow H_2O$, $K_3$. The equilibrium constant (K) of the reaction: $2NH_3 + \frac{5}{2}O_2 \rightleftharpoons 2NO + 3H_2O$, will be