In this task, you are given an input list A. You need to find all the elements of the list that are numbers and calculate their sum.
['3633', '7169', 'e', '977', '273', 'W', '9839', 'Q', '249', 'B', 'M', '4167', '8285', 'O', '685', 'u', '8629', '4511', 'g', '4129']