The managers of a large company wished to know the percentage of employees who feel "extremely satisfied" to work there. The company has roughly 24,000 employees. They contacted a random sample of employees and asked them about their job satisfaction, obtaining 437 completed responses. For each scenario, determine the sampling method used by the managers:

a) Use the company e-mail directory to contact 150 employees from among those employed for less than 5 years, 150 from among those employed for 5-10 years, and 150 from among those employed for more than 10 years.

b) Use the company e-mail directory to contact every 50th employee on the list.

c) Select several divisions of the company at random. Within each division, draw an SRS of employees to contact.