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.
['H', 'V', '9649', '977', 'G', 'b', 'r', 'n', 'a', 'o', '5107', 'T', '8017', '7903', 'o', '2009', 'P', '4289', 'W', '2931']