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.
['s', '369', 'Z', 'h', 'K', '2183', 'y', 'P', 'W', 'f', '6675', 'A', 'Z', '9159', '4179', '8695', '3015', 'o', '7321']