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.
['a', 'G', 'e', 'a', 'j', '9125', '7915', 'N', 'D', '8319', '2441', '7649', 'U', '711', 'y', 'd', 'b', '8253']