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.
['5021', 'q', '4109', 'g', 'w', 'C', 'w', '239', 'N', '9755', '8591', '7083', 'Q', '7907', 'w', 'U', 'a', '4901', 'k', 'G']