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.
['4389', '9387', 'm', 'f', 's', 'U', 'q', 'Z', 'K', 'K', 'B', 'k', '3935', '3113', 't', 'V', '4167', '9629']