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.
['j', '5001', '3933', '6609', 'I', '7379', '9613', '5521', '569', '5821', 'T', '7681', '6581', '4917', 'O', 'R', 'K', '3911', 'e']