20 . The mean yearly rainfall in Sydney , Australia, is about 137 mm and the standard deviation is about 69 mm (" Annual maximums of . " 2013 ) . ASSUME rainfall is normally distributed . ( 1 ) Find the probability that the yearly rainfall is more than 240 mm . ( II ) Find the probability that the yearly rainfall is between 140 and 250 mm . ( Ill ) If a year has a rainfall less than 10 0 mm . does that mean it is an unusually dry year ? Why or why not ?" ( iv ) What rainfall amount are 90%' of all yearly rainfalls more than ?"