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.
['c', '5709', 'M', 'B', 'D', 'a', 'e', '5251', 'r', '5911', '3327', 'B', '7191', '7107', 'J', '7257', '4531', '5507', '6617', '3429']