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.
['3513', 'K', '2035', '4057', 'A', '5149', 'Z', 'v', '3071', 'U', '6255', '7869', 'a', 'F', 'e', 'o', '911', 'k']