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.
['F', '4935', 'A', 'n', 'q', 'H', 'b', 'b', 'M', '5745', 'X', 'E', 'g', 'r', '4535', 'p', '3177', '4757', 'Z', '3449']