For the data shown in the stem-and-leaf plot, what is the effect on the mean and median of adding the value 10 to the data set? a. the mean is decreased by about 0.7 and the median is decreased by 2. b. the mean is decreased by about 0.7 and the median is decreased by 3. c. the mean is decreased by about 1.2 and the median is decreased by 2. d. the mean is decreased by about 1.2 and the median is decreased by 3.