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.
['Q', '219', 'K', 'M', 'z', '8001', '5977', '3811', 'Z', 's', 'H', '6707', '9593', 'w', '489', 'z', '4669', '7009', 'N']