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.
['k', 'g', '3273', 'A', 'r', 'r', 'I', '6171', 'k', 's', 'q', 'w', '7939', '2867', '5715', 'h', 'x', 's']