A tank can be filled with water by two pipes A and B together in 48 minutes. If Pipe A is closed after 40 minutes, the tank gets filled in a total of 60 minutes. In how many minutes can Pipe A alone fill the empty tank?

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?