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: [28.797, 188.196, 148.309, 197.013, -45.842, 189.915, 249.708]

136.585