To do a certain work, the ratio of efficiency of A to that of B is 3 : 7. Working together, they can complete the work in \(10\frac{1} {2} \)days. They work together for 8 days. 60% of the remaining work will be completed by A alone in:

Pipes A and B can fill a tank in 10 hours and 40 hours, respectively. C is an outlet pipe attached to the tank. If all the three pipes are opened simultaneously, it takes 80 minutes more time than what pipes A and B together take to fill the tank. A and B are kept opened for 7 hours and then closed and C was opened. C will now empty the tank in :

A and B can do a job in 10 days and 5 days, respectively. They worked together for two days, after which B was replaced by C and the work was finished in the next three days. How long will C alone take to finish 60% of the job?