A and B working alone can do a certain piece of work in 40 days and 120 days respectively. A and B start working together on that work but after having worked for 10 days, the work is increased. The additional work is such that B would take 40 days working alone to complete it. In order to cope with additional load, C is introduced and the remaining work is finished in 5 days. Find the number of days that C alone would take to complete the original work.

1) 8
2) 6
3) 10
4) 12