I need help working this out step by step please

X 12. 0/1 12. In a large Midwestern university (with the class of entering freshmen being on the order of 6000 or more students), an SRS of 100 entering freshmen in 1993 found that 20 finished in the bottom third of their high school class. Admission standards at the university were tightened in 1995. In 1997, an SRS of 100 entering freshmen found that 10 finished in the bottom third of their high school class. Let p, be the proportion of all entering freshmen in 1993 who graduated in the bottom third of their high school class, and let pa be the proportion of all entering freshmen in 1997 who graduated in the bottom third of their high school class. Which of the following represents 99% confidence interval for P, - Pz? a. (0.2 - 0.1) + 1.96 (0.2) (0.8) + (0.1)(0.9) 100 100 b. (0.2 - 0.1) + 1.96 (0.2)-9) (0.1)(0.9) 100 100 d. (0.2 - 0.1) + 2.576 (0.2)(0.8) (0.1)(0.9) 100 100 c. (0.2 - 0.1) + 1.96 (0.15)(0.85) (0.15) (0.85) (0.15) (0.85) (0.15)(0.85) 100 100 e. (0.2 - 0.1) + 2.576 100 100