A Cell Phone company sells cellular phones and airtime in a State. At a recent meeting, the marketing manager states that the average age of the customers is 40 years. Before actually completing the advertising plan, it was decided to select a random sample of customers. Among the questions asked in the survey of 50 customers was the customer's ages. The mean and the standard deviation of the data based on the survey are 38 years and 7 years.

a. Formulate a hypothesis to test the marketing manager's claim.

b. Does the sample support manager's claim. Test at 0.05 level of significance.