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.
['8401', 't', '497', 'G', 'N', '5813', '3081', '9603', '1029', '2247', '5265', '7255', 'C', '3227', 'y', 't', '2533', '3723', 'j']