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.
['7009', 'k', '4689', '7709', 'T', '1419', '5607', '8359', '7277', 'w', 'B', 'l', 'B', 'Q', '5615', '1607', 'f', '6957', 'D']