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: [51.66, 58.159, 168.666, -70.01, 204.748, 234.693, 137.51, 247.334, 189.8]

135.84