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: [200.289, 141.295, 69.557, 143.508, -49.059, 150.027, 39.627, 104.639, -13.318, -28.732]

75.783