$\left( 1 \right)\,{N_2}\left( g \right) + 3{H_2}\left( g \right) \rightleftharpoons 2N{H_3}\left( g \right)\,,\,{K_1}$
$\left( 2 \right)\,{N_2}\left( g \right) + {O_2}\left( g \right) \rightleftharpoons 2NO\left( g \right)\,,\,{K_2}$
$\left( 3 \right)\,{H_2}\left( g \right) + \frac{1}{2}{O_2}\left( g \right) \rightleftharpoons {H_2}O\left( g \right)\,,\,{K_3}$
The equation for the equilibrium constart of the reaction
$2N{H_3}\left( g \right) + \frac{5}{2}{O_2}\left( g \right) \rightleftharpoons 2NO\left( g \right) + 3{H_2}O\left( g \right)$
$(K_4)$ in terms of $K_1 , K_2$ , and $K_3$ is