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: [165.78, -65.839, -70.05, -8.504, -77.289, 141.978, -2.607, -86.849, 92.431, 209.984]

29.904