thanks for reply.
i am using the book Serway and Jewett. There for the heat pump, instead of efficiency , he talks about
coefficient of performance(COP) defined as
and he says that , because
is generally greater than W , typical values of COP are greater than unity.
So how do I relate the efficiency to this ?
Edit: I checked the answer key and it gives 1000 J as the correct answer. Though in my first post , I could find the
upper bound for the W as 1000 J, the answer IS 1000 J. So is it possible that the problem wanted to ask "greatest amount of
work" instead of "smallest amount of work" ?