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.
['9177', '455', '8791', '7359', '6297', 't', '6833', '9609', 'b', 'M', 'D', '233', 'U', '8551', 'U', 'u', 'V', '963', '5377']