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.
['6033', '649', 'F', 'H', '3233', 'J', '5603', '403', 'C', '7503', '8187', 'r', 'F', 'A', 'B', 'w', '7727', '987', '4529']