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.
['5903', '2503', '8387', '7135', '9145', 'm', '4583', '9399', 'X', '6941', 'x', '6049', '3105', 'o', '3179', '3877', '2409', 'q']