33. One mole of ideal monoatomic gas

[γ=(5/3)]  is mixed with one mole of diatomic gas [γ=(5/3)].  What is γ  for the mixture? γ denotes the ratio of specific heat at constant pressure, to that at constant volume

(a)  3/2                                     (b)  23/15

(c)   35/23                                (d)  4/3

Answer-a