The volumetric properties of two gases M and N are described by the generalized compressibility chart which expresses the compressibility factor (Z) as a function of reduced pressure and reduced temperature only. The operating pressure (P) and temperature (T) of two gases M and N along with their critical properties (P_c, T_c) are given in the table below. Z_M and Z_N are the compressibility factor of the gases M and N under the given operating conditions, respectively. The relation between Z_M and Z_N is