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.
['251', 'T', 'k', 'M', '8739', '9073', '1275', '8825', 'Q', '4387', '2583', 'l', 'x', '8341', 'C', '8981', '9857', 'Q']