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.
['R', 'b', 'V', '3005', '1807', '3091', 'q', 'u', 'W', 'h', 'o', 'B', 'K', '6615', 'F', 'V', '9767', '6783']