A company attempts to evaluate the potential for a new bonus plan and decides to use the bonus plan for a trial period. The weekly sales volume achieved by a sample of 4 salespersons before and after implementing the bonus plan is shown below. (For the following matched samples, let the difference d = After - Before.) Weekly Sales (in units) Salesperson Before After 1 48 44 2 48 40 3 38 36 4 44 50 Assume the population of differences is normally distributed. a. State the hypotheses. b. Compute the test statistic. c. Use = .05 and test to see if the bonus plan will result in an increase in the mean weekly sales for the company.