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.
['4781', '9203', '2367', '8509', 'S', '367', 'L', 'q', 'I', 'g', '2087', '6125', 'X', 'r', '3943', 'D', 'v', 'Q']