A train was moving at 50m/s and slow down to 20 m/s in 50 seconds, what was its acceleration?

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