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.
['q', '7505', 'H', 'Z', 'c', '4521', '83', 'g', '701', 'h', 'B', '3099', '1735', '7727', 'N', 'z', '8777', 'P']