Working 10 hours a day, 2 pumps can empty a tank in 4 days. If the number of pumps is tripled, how many hours a day must they work to empty the tank in exactly 1 day? (Round to the next higher hour if needed)

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?