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.
['5599', 'I', '5055', '4105', '263', '4677', 'M', '5269', 'k', 'n', '8373', 'i', '4715', 'O', 'd', '8187', 'F', '7465', '8103']