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: [209.13, -12.632, 247.489, 55.492, 8.967, -90.158, 193.743]

87.433