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.
['w', '4789', '2025', 'V', 'Q', '8009', '1831', '8947', '7601', 'z', '5477', '6337', 'V', 'Y', '8207', 'z', 'p', 'f']