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.
['9077', '625', 'S', 'S', 'w', 'z', '2891', 'X', 'E', 'K', '6153', '5877', 't', 'v', '9219', '6639', 'N', 'C']