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.
['1725', '5671', 'L', 'R', '9131', '1511', '2781', 'Y', 'f', '9531', '777', 'w', 'E', 'l', 'f', '601', 'O', '7033', 'd']