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.
['1527', '4209', 'o', '7877', 'w', '5421', '8827', '5139', 'H', '1939', '4923', '6025', '9369', '1481', '7889', 'Q', 'l']