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.
['Z', 'X', '3595', '6405', '5967', 'y', '8219', 'W', 'W', 'I', 'Z', '3325', 'N', '4687', '7387', 'r', '6477', '777', '6467', '3341']