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.
['3043', 'a', 'j', '4069', 'B', '6573', '3493', '3861', 'E', 'A', 'O', '8539', '5731', '3471', 'L', 'a', 'I', '4141']