Would sound travel faster through a gas that is 90% nitrogen and 10% helium or through a gas that is 90% helium and 10% gas

On your wedding day your lover gives you a gold ring of mass 3.67 g. 48 years later its mass is 3.44 g. on the average how many atoms were abrated from the ring during each second of your marriage? the atomic mass of gold is 197 u. don't enter units