please help this probability and statistics questions with clear steps and explanation, thankssss, i need Q4 to Q6 only, Q1 and 3 solved, thankssss

Experience indicates that a monthly long-distance telephone bills is normally distributed with a mean of US$17.85 and a standard deviation of US$3.39. After an advertising campaign aimed at increasing long-distance telephone usage, the manager of the US telephone company took a random sample of 25 household bills and recorded their monthly usage. The results are listed below. 19.61 20.14 19.57 19.26 14.03 19.24 15.98 24.85 26 19.46 18.29 16.91 26.15 19.64 16.75 20.52 25.47 18.19 12.56 28.47 14.13 19.72 17.05 13.92 12.38 Do the data allow us to infer at 5% significance level that the campaign was successful? Answer Questions 1-3 below. Question 1: (1 Mark) State the null and alternative hypotheses. Question 2: (1 Mark) Find the value of the test statistics. Question 3: (1 Mark) Indicate the rejection region and state the conclusion. Assume now that a monthly long-distance telephone bills is normally distributed with a mean of US$17.85, but the population standard deviation is unknown. For the same random sample shown in Questions 1-3, do the data allow us to infer at 5% significance level that the campaign was successful? Answer Questions 4-6 below. Question 4: (1 Mark) State the null and alternative hypotheses. Question 5: (1 Mark) Find the value of the test statistics. Question 6: (1 Mark) Indicate the rejection region and state the conclusion