Each city arrest 30*10=<<30*10=300>>300 people during the protest
So a total of 300*21=<<300*21=6300>>6300 people were arrested
They spend 14/2=<<14/2=7>>7 days of their sentence in jail
So they spend a total of 7+4=<<7+4=11>>11 days in jail
So there was a total of 6300*11=<<6300*11=69300>>69300 days in jail
So they spent 69300/7=<<69300/7=9900>>9900 weeks in jail
#### 9900