The relative humidity (in %) of air sample is

Question

A moist air sample has dry bulb temperature of 30⁰C and specific humidity of 11.5 g water vapour per kg dry air. Assume molecular weight of air as 28.93. If the saturation vapour pressure of water at 30⁰C is 4.24 kPa and the total pressure 90 kPa, then the relative humidity (in %) of air sample is 

      (a) 50.5                                                                (b) 38.5

      (c) 56.5                                                                (d) 68.5