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.

['6921', 'a', 'U', '2821', '2111', 'h', '3937', '3697', 'd', '6309', 'q', '7961', '5287', '5375', '2721', '4523', 'V', '8633', 'c', '7643']
67939

['y', 'p', '3553', '2155', 'b', 'R', 'j', 'V', 'U']
5708

['d', 'Q', '5491', 'l', '6621', '7733', 'T', 'a']

19845