Some people who bought X-Game gaming systems over the holidays have complained that the systems they purchased were defective. In a sample of 1200 units sold, 24 units were defective.

a. What is the sample porportion?

b. Determine a 95% confidence interval for the percentage of defective systems.

c. If you want the margin of estimate error over the defective proportion to be within 0.5% margin of error (with the same confidence of 95%), how many units should be sampled?