After taking a random start between 1 and 20 and then taking every 20th element from the sampling ...

After taking a random start between 1 and 20 and then taking every 20th element from the sampling frame, Smith learned that 40 of the sample believed the company's president was doing a good job. The calculated standard error was 3 percent. Assuming a normal distribution, this means that
 
  a. between 37 and 43 of the employees believe the president is doing a good job.
  b. you are 95 certain that between 37 and 43 of the employees believe the president is doing a good job.
  c. you are 68 certain that between 37 and 43 of the employees believe the president is doing a good job.
  d. you are 99 certain that between 37 and 43 of the employees believe the president is doing a good job.
  e. between one and twenty percent of the sample believes the president is doing a good job.