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.
['2287', 'J', '6031', 'v', '373', '2805', 'g', 'K', '2843', '8915', 'u', 'b', 'm', '2545', '4635', '749', 'w', 'O', 's', '1157']