Krishn has 1 hour to clean the house before his parents get back from their holiday. He has to hoover 3 rooms, clean out his pet hamster's cage and wipe off the drawing of an elephant he accidently did on the bathroom wall. Each room takes 12 minutes to hoover, it takes 18 minutes to clean out his hamster's cage and 21 minutes to rub out the elephant, which he does last. What fraction of the elephant is left on the wall when Krishn's parents arrive home?​