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.
['7997', 'u', 'V', '2905', 'h', 'O', '8993', '6347', 'x', '6157', '9067', '8801', '8417', '5259', 'J', 'N', '1815', 'o']