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.
['3353', '107', '7043', '8049', '1711', '3421', 'T', '4275', 'e', '177', '1383', 'J', 'F', '1087', 'L', 'u', '8725', '29', '615']