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.
['6025', 'Z', 'B', '5717', '9649', '1223', 'i', 'z', '3981', 'I', '8297', 'O', 'D', '8707', '9751', 'r', 'P', 'G']