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.
['5419', '8073', '3449', 'z', '8337', 'Y', 't', 'j', 'y', '5295', '4309', '9885', '9205', 'j', 'k', '6461', '505', 'b', '8437']