Medicare Would Like to Test the Hypothesis That the Average $$z \bar { x }$$

Medicare would like to test the hypothesis that the average monthly rate for one-bedroom assisted-living facility is equal to $3,300. A random sample of 12 assisted-living facilities had an average rate of $3,690 per month. The standard deviation for this sample was $530. Medicare would like to set ? = 0.05. The test statistic for this hypothesis test would be .

A) $$z \bar { x }$$ = - 1.37
B) $$t \bar { x }$$ = 2.55
C) $$z \bar { x }$$ = 1.98
D) $$t \bar { x }$$ = - 2.16