The mean potassium content of a popular sports drink is listed as 140 mg in a 32-oz bottle. Analysis of 28 bottles indicates a sample mean of 139.5 mg.

(a)Assuming a known standard deviation of 1.8 mg, calculate the z test statistic to test the manufacturer's claim.(Round your answer to 2 decimal places. A negative value should be indicated by a minus sign.)

Test statistic_____?______

(b)Find the p-value .(Round intermediate calculations to 2 decimal places. Round your answer to 4 decimal places.)

p-value______?_______