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.
['C', 'q', '1899', '2055', '7497', '2225', '4379', 'c', 'B', 'l', 'e', 'M', '3073', 'M', 'R', '9687', 'j', 'I', '8625', '7413']