The lapping process which is used to grind certain silicon wafers to the proper thickness is acceptable only if σ, the population standard deviation of the thickness of dice cut from the wafers, is at most 0.50 mil. Use the 0.05 level of significance to test the null hypothesis σ = 0.50 against the alternative hypothesis σ >0.50, if the thicknesses of 15 dice cut from such wafers have a standard deviation of 0.64 mil. Calculate the test statistic correct to two decimal places.