A 50.0 g block of copper whose temperature is 400 K is
placed in an insulating box with a 100 g block of lead whose temperature
is 200 K. (a) What is the equilibrium temperature of the
two-block system? (b) What is the change in the internal energy of
the system between the initial state and the equilibrium state? (c)
What is the change in the entropy of the system?