Asurvey asked 30 people if they believed that private enterprise could solve us problems 14 said yes. which of the following statements correctly describes how the confidence interval for the population proportion of people that agree that private enterprise can solve us problems should be computed?

(a) there are at least 15 successes and 15 failures. a large sample confidence interval for the population proportion can be computed (phat +/- z * sqrt(p*(1-p)/n) with no additional values added.
(b) there are not 15 successes and 15 failures. a confidence interval can not be done.
(c) there are not 15 successes and 15 failures. a confidence interval can be computed by adding 2 successes and 2 failures.
(d) there are not 15 successes and 15 failures. a confidence interval can be computed by adding 1 success and 1 failure.