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.
['l', 'j', 'E', '7833', 'E', 'g', '945', '437', '1313', '2277', 'o', 'r', 'e', '2557', '5231', 'y', '729', '1761', '981', '9441']