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', 'B', '5953', '5249', '1215', '5409', 'Q', '747', '4815', '5825', '205', 'i', 'S', 'y', '9849', 'P', 't', 'z']