We have discussed the density of states (Z(E)) and the Fermi-Dirac distribution (F(E)). (1) What is the physical meaning of Z(E)F(E)? (7 pts) (2) Plot the Z(E)F(E) curve below if the temperature T = 300K; (7 pts) (3) On the Z(E)F(E) curve at T = 300K, mark the "eligible" electrons for emission; (7 pts) (4) Redraw the Z(E)F(E) curve for T = 500K and provide an explanation on its difference from the curve for T = 300K. (7 pts