Which statement correctly describes how energy input and efficiency relate in a boiler?

Which statement correctly describes how energy input and efficiency relate in a boiler?

• A. Energy input equals mass flow times higher heating value; efficiency determines how much useful energy is recovered in the steam.
• B. Energy input equals mass flow times lower heating value; efficiency determines boiler pressure.
• C. Energy input equals mass flow times lower heating value; efficiency determines how much of that input becomes useful steam energy.
• D. Energy input equals mass flow times lower heating value; efficiency determines heat losses.

Answer: (C)