In order to compare the performance of students in large enrollment and small enrollment sections, 35 students from large sections and 35 students from small sections of a freshman mathematics course were randomly selected. The mean and sample standard deviation of grades on the common final exam for the students from large sections were 72.8 and 7.4; for the students from small sections, the mean and standard deviation were 75.3 and 6.8. A 90% confidence interval for the difference in the mean common final exam scores between students in the two types of sections is about: