A can do a piece of work in 40 days; B can do the same in 30 days. A started alone but left the work after 10 days, then B worked at it for 10 days. C finished the remaining work in 10 days. C alone can do the whole work in?
1
24 days
2
30 days
3
44 days
4
17\(\frac {1}{2}\) days