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.
['m', '6721', '7861', '1853', 'E', '8163', '3717', '7053', '8625', '4949', '9865', '3685', 'Y', 't', '5593', 'b', '6529', '9087', '4181']