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.
['6973', '5487', '5969', 'W', '6141', 'I', 'z', '5291', 'v', 'b', 'e', 'I', 't', '2547', 'c', 'd', 'g', 'b', '9']