The difference in enthalpy of ammonia as a fluid at saturation conditions at 1165.8 kPa abs and 236.2 kPa abs is found in the:

The enthalpy difference of ammonia in a saturated state at specific pressures can be determined using the steam tables or refrigerant tables, which provide the thermodynamic properties for various substances. In the context of this question, we are looking for the enthalpy difference specifically at saturation conditions for a given pressure, identified as the hf (enthalpy of the saturated liquid) value for two different pressures.

At saturation conditions, hn refers to the enthalpy of the fluid (saturated liquid), whereas hg refers to the enthalpy of the saturated vapor (gaseous form). The hf column lists the enthalpy of the saturated liquid, which is crucial for calculating differences in enthalpy when moving from one pressure to another under saturation conditions.

The calculation that results in a difference of 208.9 kJ/kg suggests that by subtracting the hf values at the two pressures (1165.8 kPa abs and 236.2 kPa abs), one can arrive at a defined change of enthalpy within the liquid phase (hf). This value represents the energy per unit mass needed to vaporize the liquid or the energy dynamics involved with the phase change under the specified conditions.

The other options pertain to different interpretations or combinations