In the ancient city of Portheus, the emperor has installed an overhead tank that is filled by two pumps - X and Y. X can fill the tank in 12 hours while Y can fill the tank in 15 hours. There is a pipe Z which can empty the tank in 10 hours. Both the pumps are opened simultaneously. The supervisor of the tank, before going out on a work, asks his assistant to open Z when the tank is exactly 40% filled so that tank is exactly filled up by the time he is back. If he starts X and Y at exactly 11:00 AM and he comes back atA:B. Then find the value of A+ B.