Thermodynamics

What is enthalpy of formation of \(\mathrm{NH}_3\) if bond enthalpies are as \((\mathrm{N} \equiv \mathrm{N})=941 \mathrm{~kJ},(\mathrm{H}-\mathrm{H})=436 \mathrm{~kJ},(\mathrm{N}-\mathrm{H})=389 \mathrm{~kJ}\) ?