$2$

This is a simpler version of Ex$.4\mathrm{.}11$ in the book.

A rigid tank has saturated ammonia with quality $\backslash (2\backslash \%\backslash )$ all mass at $40$ C $.$ We now withdraw half the mass from the top of the tank with a pipe and valve to an external system. This happens slowly enough so heat transfer to the tank keeps the temperature constant. Find the heat transfer.