A research scientist would like to estimate the tensile strength of a newly created synthetic fiber. He would like to estimate the mean strength to within 2 pounds with 90% confidence. In a preliminary study, he estimates the standard deviation to be 35. What sample size should the research scientist use? Problem 3, (34 points) Eight hundred (800) high school freshmen were randomly selected for a national survey. Among survey participants, the mean grade-point average (GPA) was 2.6, and the standard deviation was 0.4. What is the margin of error, assuming a 95% confidence level? (Show all your works, if you just only indicate correct answer, you will get only 5 points)