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.
['V', '7551', 'T', 'm', '999', 'Y', 'B', 'i', 'F', '8355', '9711', 'l', '2693', '1979', 'G', 'B', '2239', '5533', '2451']