Must the amount of heat absorbed as 1 kg of saturated liquid water boils at 100 °c, be equal to the amount of heat released as 1 kg of saturated water vapor condenses at 100 °c? why?

Which of the following ziegler nichols tuning methods the response of the controller to a step input should exhibit an s-shaped curve? a)-open loop mode b)-closed loop mode c)-both modes (open & closed) d)-none of the modes (open & closed)