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.
['6225', '8821', '7183', '2439', 'w', '1457', '7449', '3803', '7681', 'k', '4045', 'v', '5903', 'q', 'q', '5183', 'k', 'Y', 'B', '7179']