A statistics instructor kept track of students' grades on her final examination and whether they did the exam in pencil or in pen. Of the 75 students who used a pencil, 62 got grades of 70% or higher. Of the 19 students who used a pen, 9 got grades of 70% or higher. Assume that these students can be considered random samples from the students who could take this instructor's final examination.

Find a 99% confidence interval for the difference in the population proportions scoring about 70% for the two types of writing utensils. (Let group 1 represent those who used a pencil.)