Textbook question. Need help in understanding how this is done. Not using for work other then to further understand the subject.

8.30 Suppose that, in a survey of 600 employers, 126 indicate that

they have used a recruitment service within the past two

months to find new staff.

a. Construct a 95% confidence interval for the population

proportion of employers who have used a recruitment

service within the past two months to find new staff.

b. Construct a 99% confidence interval for the population

proportion of employers who have used a recruitment

service within the past two months to find new staff.