Answer: -
24 grams per kilogram.
Explanation: -
We know that
The mixing ratio = actual (measured) mass of water vapor (in parcel) in grams / mass of dry (non water vapor) air (in parcel) in kilogram
The saturation mixing ratio = mass of water vapor required for saturation (in parcel) in grams/ mass of dry (non water vapor) air (in parcel) in kilograms
Relative humidity = actual (measured) water vapor content/ maximum possible water vapor amount (saturation)
Thus saturation mixing ratio = Mixing ratio / relative humidity
= 6 / (25/100)
= 24