Sixty-one students were asked at random how much they spent for classroom textbooks this semester. The sample standard deviation was found to be 8 - $28.70. How many more students should be included in the sample to be 99% sure that the sample mean is within $7 of the population mean for all students at this college? 6. (a)0 (b) 65 (c)51 (d)4 (e)112