An on-line retailing firm conducts a study into the number of on-line purchases of footwear made during all of last year. The study wants to determine the proportion of Australians over the age of 25 who purchase footwear on-line. The managing director of the on-line retailing firm believes this proportion of Australians is 31%. A random sample of 199 Australians over the age of 25 is selected. If the managing director's claim is true, what is the sample proportion value below which 10% of all sample proportions would exist? Express your answer correct to two decimal places.