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', 'r', 'E', 'r', 'L', '9447', '8759', '2097', 'G', '8693', '1631', '7387', 'W', '231', '8507', '5975', '5175', '7807', 'y']