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.
['6249', '5411', '509', 'g', 'F', 'P', 'r', 'C', '3427', '4239', 'y', 'l', 'T', 'b', 'o', 'x', '6907', '6277', 'W', 'V']