In a study of government financial aid for college​ students, it becomes necessary to estimate the percentage of​ full-time college students who earn a​ bachelor's degree in four years or less. Find the sample size needed to estimate that percentage. Use a 0.04 margin of error and use a confidence level of 95 % . Assume prior studies have shown that about ​40% of​ full-time students earn​ bachelor's degrees in four years or less.