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.
['9679', 'O', '9791', 'b', '3837', 'Y', 'f', '771', '6155', 'j', 'Q', 'f', 'n', '9197', '6781', 'v', '7271', '2893', '3065', 'u']