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.
['j', 'J', 'b', '8341', 'T', '377', 'L', 'O', 'c', 'j', '7291', 'T', 'f', 'E', 'D', '873', '9197', '1877']