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.
['D', '7807', '9395', 'T', 'c', '5139', '2827', 't', 'T', 'm', '3717', 'U', '3225', '7419', '2481', 'p', 'C', '5277']