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.
['8493', '6917', '5193', 'h', 'G', '737', '4577', '4621', '1179', 'p', 'z', 'u', 'V', '5079', 'b', 'j', '5475', '6917', 't', 'D']