A boy starts to paint a fence on one day. On the second day, two more boys join him. On the third day, three more boys join the group and on the fourth day four more boys join the group and so on. If the fence is completely painted this way in exactly 20 days, then find the number of days in which 10 men painting together can paint the fence completely, given that every man can paint twice as fast as a boy can.

1) 154
2) 77
3) 20
4) 45