The cold air standard value of = 1.4 was based on the heat capacity of a

The cold air standard value of γ = 1.4 was based on the heat capacity of a diatomic gas with no vibrational excitation (see §9), C_V = 5/2 nR and C_p = C_V + nR. In reality, the heat capacity increases with increased temperature, and γ decreases accordingly. If we assume, however, that CV is independent of temperature through the cycle and that C_p = C_V + nR remains valid, what value of C_V is required for γ = 1.3?