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.
['4279', 'B', '3453', 'I', 'T', 'Q', '8603', '9395', '4083', '101', '2083', '6253', 'q', 'f', '2855', 's', '951', '665', 'O']