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.
['B', 'C', '8375', 'K', 'P', 'F', '6065', '5801', 'f', 'H', 'm', '4543', 'S', 'H', '6919', 'R', 's', 'j', '1997', 'V']