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.
['C', '9223', '5853', '1649', '5303', '9689', '6591', '8739', 'k', 'M', '4289', '8835', '4675', '9571', '7775', '7193', '9683', '3569', '7881']