Definition: In this task you will be given a list of numbers and you need to find the mean (average) of that list. The mean of a list can be found by summing every number in the list then dividing the result by the size of that list. The output should be rounded to 3 decimal places.
Input: [120.014, 56.117, 156.463, 48.553, 51.746, 239.968, 138.174]

115.862