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.
['8903', 'E', '9711', 'm', '8855', '8203', 'B', 'P', '801', 'E', '2613', 'W', '4415', '3847', '7697', '5603', 'F', 'f', 'B']