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.
['1857', 'n', '1337', '1473', 'K', '4725', '8819', '4357', 'X', '957', 'x', '3783', 'd', '6185', '5919', 'C', '5617', '1125']