In this case, we need to remember that the second law of thermodynamics states that heat flow is transferred from a hot object to a cold object only, never the other way around, therefore, the answer is c) will never be spontaneous at any pressure. This is supported by driving force that in this case is the temperature difference which must be negative for the hot object (it gets eventually cold) and positive for the cold object (it gets eventually hot) until they reach the equilibrium temperature.
Phosphorus is in group VA so it has 5 valence electrons and Oxygen is in group VIA so each oxygen has 6 valence electrons. Total valence electrons = 5 + 4(6) = 29