7.1 The professor of a large calculus class randomly selected 6 students and asked the amount of time (in hours) spent for his course per week. The data are given below. 10 8 9 7 11 13 a. Estimate the mean of the time spent in a week for this course by the students who are taking this course. b. Estimate the standard deviation of the time spent in a week for this course by the students who are taking this course. c. Estimate the standard error of the estimated mean time spent in a week for this course by the students who are taking this course.