Three friends who met at university had an average age of 20 at the time they met. After a certain period of time, these three friends gathered together with one child each, and it was observed that the average age of these six people was again 20.
It is known that the age differences between these three friends and their children are 28, 30, and 32.
Accordingly, how many years after the three friends met did they gather together?
A) 15\\
B) 16\\
C) 18\\
D) 20\\
E) 21