KöMaL 2018 K572

Tom Sawyer and Huckleberry Finn were painting the fence together. It would take Tom 3 hours to paint the whole fence alone, and it would take Huck 4 hours to do it alone. However, when they work together, their working speed decreases by 20% since they are doing pranks on each other continually. The two of them started working at noon, but after a while Huck was getting bored, so he decided to go fishing instead. Tom spent 10 minutes trying to persuade him to continue (during that time, neither of them did any painting at all), without success. So he threw a dead rat at Huck, and finished the job alone. He was done at 2:34. When did Huckleberry Finn stop painting?