You have poverty guidelines for a certain msa which indicate that for a family of four the weekly income necessary to be above the poverty line is $550. You take a sample of household incomes for 48 households zoned for a particular school within the msa. You find a sample average for weekly income of $540 and a standard deviation of $86. Test the null hypothesis that average weekly pay for households zoned for that school is at least $550. Conduct this test at the. 05 level of significance. What is the critical value? answer to four decimal places.