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.
['y', '7973', 'F', 'V', 'w', 'D', '9841', 'f', '9315', 'M', 'D', 'V', '2327', 'K', 'w', 'D', 'r', '1413']