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.
['6303', '3145', 'i', 'm', '9985', 'c', 'D', 'h', '7711', 'F', 'Z', '6939', '8955', '2485', '4519', '4335', 'Y', 'M', 'y', 'g']