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: [85.793, 139.002, -48.149, -17.676, 176.457, 148.934, -17.472, 61.563, -89.914]

48.726