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.
['Q', 'P', 'Y', 'G', 'b', '2293', 'j', '763', 'U', '841', 'y', '8607', '7261', '6451', 'm', '8027', 'G', 'Z']