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.
['n', 'X', 'Q', '2735', '515', '6647', '9335', 'F', 'a', 'C', '1879', '3865', '4317', '709', '5849', 'u', 'G', 'V']