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.
['355', '4545', '3073', 'U', '8437', '1105', '189', '1351', 'G', 'q', '9069', 'w', 'Y', 'k', 'x', '1463', '1823', '531', '5983']