Help finding solutions

A public health researcher wants to know whether a new tax that was placed on soda has had any impact on people's behavior. Before the new tax, convenience stores in the city sold an average of u = 410, sugar filled beverages per day with o = 60. The distribution was normal. Following the new tax, data were collected for a sample of n = 9 days and the new mean was M = 386 from the same convenience stores. 11. What is the standard error (o ) for the above scenario? a. 60 b. 30 c. 20 d. Cannot determine 12. What is the z-score for the above scenario? a. - 1.20 b. + 1.20 c. -.80 d. .80 13. Using a two-tailed test with a .05 significance level, can you conclude there was a significant change in people's behavior? a. Yes b. No c. Cannot determine