The mean is the average.
Add the number of contacts and divide by the number of people:
112 + 104 + 96 + 54 +98 +120 = 584
584 / 6 = 97.3
The mean = 97.3
Now add the standard deviation to the mean for the higher value and subtract the standard deviation from the mean for the lower value:
97.3 - 21 = 76.3
97.3 +21 = 118.3
The answer would be D.