Statistics and Probability

In a recent survey of - students, one of the question was \"Have you been reviewing the materials of the course regularly?.\" (a) Find the number of students that need to be surveyed so that the error estimate a of the survey is smaller than 10% with 95% condence. (b) Suppose that the result of the survey was that 60% of the participants answered \"yes\" to the question. The friendly instructor wants another survey to get a result that is more accurate. How many more people did he need to survey so that the error estimate a of the survey is smaller than 5% with 95% condence