16 men can finish a piece of work in 8 days, while 20 women and 4 men together can complete the same work in 16 days. In how many days can 10 women complete the entire work working by themselves?

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?