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.
['5415', 'u', '4377', '2147', '3927', '7989', '6677', 'n', '8035', 'z', 'f', '5347', '3361', 'l', 'C', 'A', 'r', '4265', '9053', '5371']