A and B undertake a contract to complete a work for Rs. 500. A can do the work in 30 days and B in 60 days. With the help of C, they complete the work in 9 days. How much should C be paid for his contribution?

If P and Q together can complete a piece of work in 15 days and P alone can do it in 45 days, in how many days can Q alone complete that work?

A can lay a railway track between two stations in 16 days and B can do the same job in 12 days. With the help of C, they finished the job in 4 days. In how many days can C alone do the job?