When the total heat of steam is h kJ/kg and the sensible heat of feed water is hf1 kJ/kg, then the factor of evaporation is given by

• A. <img src="/_files/images/mechanical-engineering/steam-boilers-and-engines/287-111-1.png">
• B. <img src="/_files/images/mechanical-engineering/steam-boilers-and-engines/287-111-2.png">
• C. <img src="/_files/images/mechanical-engineering/steam-boilers-and-engines/287-111-3.png">
• D. none of these