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.
['3943', '457', 'B', '5647', '603', 'o', 'E', '4825', 'I', 'I', '1973', 'J', 'c', 'o', '7497', 'X', '4747', '8369']