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.
['v', '9433', 'r', '8829', 'P', 'w', 'm', 'T', '7601', '7719', '789', 'A', '5789', 'l', '2859', '9875', '2631', 'y', '6397', 'i']