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.
['E', '5775', '1595', 'b', 'm', '3709', 'l', '6879', 'O', '2337', '8549', '5415', 'j', '3365', 't', '2351', '4707', '8309']