2.70 Fifteen randomly selected college students were asked to state the number of hours they slept the previous night. The resulting data values are 5, 6, 6, 8, 7, 7, 9, 5, 4, 8, 11, 6, 7, 8, 7. Find the following:

a. mean, ¯ x

b. median, ˜ x

c. mode

d. midrange