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.
['1867', '5301', 'x', '3867', '8707', '2429', 'K', '59', '6629', 'v', 'A', 'y', 'P', '3829', '1979', 'R', '8481', '5767', 'h', 'U']