A district sales manager wishes to determine whether there is a difference In mean dally sales volume between two stores in his district. He collects daily sales volume for the month of June to do the analysis. Assume that the population standard deviations are unknown and unequal. The hypothesis test is to be conducted using the 0.01 level of significance. Partial output of his results from Excel can be found in the table below: Store 1 Store 2 Sample size (n) 30 30 Sample mean daily sales volume (in $1,000) 15 19 Sample standard deviation (in $1,000) 5.2 6.1 Degrees of freedom 56 What is the critical value of the test statistic?