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.
['P', 'B', '5503', 'S', '5981', '4185', 'I', 'I', 'a', '9193', 'q', 'I', 'z', 'J', 'I', '717', '6015', 'y']