In order to study the amounts owed to the city council, a city clerk takes a random sample of 16 accounts from a large number of delinquent accounts and finds the average amount owed to the city to be $239. It has been claimed that the true mean amount owed on accounts of this type is greater than $250. If it is appropriate to assume that the amount owed is a normally distributed random variable with a standard deviation of $35, then the value of the test statistic appropriate for testing the claim is: (Your answer should be correct to two decimal places.)