The heat of combustion of CH4(g), C (graphite) and H4 (g) are respectively −20k.cal, −40k.cal and −10k.cal. The heat of formation of CH4 is
If x K.cal and y K.cals are the ΔH values of ionisation of weak acid (WA) and weak base (WB) respectively,ΔH of neutralisation of the WA and WB is