HELP!:Real-World Heat Transfer, heating water .... Can someone help me with this problem? Suppose you have a carton of milk out of the fridge. It is most energy efficient to: a.) immediately return it to the fridge b.) leave it out as long as possible I am not sure whether this has to do with latent heat of vaporization of latent heat of fusion. Can anyone please help me on this? I'm new to this so i only have introductory knowledge on this topic.