What is heat of atomisation of ${\mathrm{P}}_4{\mathrm{O}}_6\left(s\right)$? Given heat of sublimation of ${\mathrm{P}}_4{\mathrm{O}}_6$ is $\mathrm{x} \mathrm{kJ}/\mathrm{mol}$ and $\mathrm{P}-\mathrm{O}$ bond energy is $\mathrm{y} \mathrm{kJ}/\mathrm{mol}$