A machine P can print one lakh books in 8 hours, machine Q can print the same number of books in 10 hours while machine R can print them in 12 hours. All the machines are started at 9 a.m. while machine P is closed at 11 a.m. and the remaining two machines complete the work. Approximately at what time will the work be finished? a. `11 : 30\ a.m.` b. `12` noon c. `12 : 30\ p.m.` d. `1\ p.m.`