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', 'Z', '1135', '6725', 'd', 'A', 'g', '1997', 'b', '9505', 'L', '8887', '8647', '8965', 'N', 'u', '2103', 'l']