A pharmaceutical manufacturer is concerned about the impurity concentration in pills, and it is anxious that this concentration not exceed 3%. It is known that in any production run the impurity concentrations follow a normal distribution. A random sample of 25 pills from a production run was checked and the sample mean impurity concentration was found to be 3.53%. The sample standard deviation was 0.21%. Test the null hypothesis that the population mean impurity concentration is 3% against the alternative that it is more than 3%. Use a 5% significance level. Answer the following, and round off your answer to three decimal places.

(a)What is the test statistic used in the decision rule?

(b)What is the critical value?