The HR manager of a large department store believes the number of resignations per week of casual staff at the store can be approximated by a normal distribution with a mean of 25 resignations per week and variance 66.7 (resignations per week)² . From a large amount of historical data available on the HR database regarding weekly resignations of casuals, a sample of 52 weeks was selected. What must the value of the sample mean be so that only 15% of all possible sample means (of size 52) are less than this value? Give your answer correct to 2 decimal places.