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.
['1203', '2067', '5601', 'i', 'k', 'A', '5255', '5829', 'l', 'h', 'S', '7185', 'R', 'z', 't', 'N', 'K', 'X', 'b']