A group of soldiers was put on a job. On second day, the Lieutenant, realizing the urgency of the work, put in 6 more soldiers. Due to further pressure, workforce had to be increased by 6, each subsequent day and the job ultimately was completed in as many days as the number of soldiers in the group at the start of the work. Had there been no addition in workforce, it would have taken 3 times as many days for completing the job. How many soldiers in all worked on this job?

1) 3
2) 27
3) 9
4) 15