K People were polled on how many books they read the previous year. Initial survey results indicate that s = 16.6 books. Complete parts (a) through (d) below Click the icon to view a partial table of critical values. (a) How many subjects are needed to estimate the mean number of books read the previous year within four books with 95% confidence? This 95% confidence level requires 67 subjects. (Round up to the nearest subject.) (b) How many subjects are needed to estimate the mean number of books read the previous year within two books with 95% confidence? This 95% confidence level requires 265 subjects. (Round up to the nearest subject) (c) What effect does doubling the required accuracy have on the sample size? Doubling the required accuracy nearly quarters the sample size. Doubling the required accuracy nearly halves the sample size. Doubling the required accuracy nearly quadruples the sample size. D Doubling the required accuracy nearly doubles the sample size. (d) How many subjects are needed to estimate the mean number of books read the previous year within four books with 99% confidence? This 90% confidence level requires subjects. (Round up to the nearest subject.)