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: [213.816, 178.027, 65.849, -91.646, 174.169, -12.033, 48.904, 148.142, 220.714, 218.252]

116.419