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: [108.874, 56.014, 148.045, 246.685, 115.853, -2.791, 249.053, -51.407, 231.081, 57.763]

115.917