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.
['K', '6803', '1755', 'D', 'V', '9343', 'B', '3003', '8699', '3325', '903', 'k', 'b', '7031', 'c', '5823', 'k', 'V', 'p', '1963']