Textbooks are getting more expensive for undergraduate students. Your local community college wants to take a SRS of undergraduate students to find out how much money they spend on textbooks. The college wants to construct a 90% confidence interval with a margin of error of less than $5. Based on last year's data, they estimate the population standard deviation to be $45. What are the minimum number of students the college needs to sample in order to have this margin of error? A. 210 B. 220 C. 230 D. 240 E. 250