please help with this question

9.2.43 Question Help 7 People were polled on how many books they read the previous year. Initial survey results indicate that s = 11.1 books. Complete parts (a) through (d) below. a 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 90% condence? This 90% condence level requires |:| subjects. (Round up to the nearest subject.) 0 Partial Critical Value Table - X Level of Condence, Area in Each Tail, Critical Value, 2\"\" (1 - a) . 100% 90% 95% 99%