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', '3405', 'z', 'l', '8179', '8621', '9499', '6679', '7815', 's', '5955', 'E', '1515', 'c', 'E', 'R', '1489', 'O', '3433']