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.
['T', 'Q', '8903', 'D', '4817', '3857', '6621', 'K', 'd', '9469', '9711', '4925', '7943', '6883', 'c', 'C', 'i', '7989', '8123', 'Q']