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.
['9793', 'a', 'h', '4117', '8267', '5981', 'r', 'W', '8557', '8657', 'k', 'F', '4087', 'o', 'H', 'q', 'j', '9047', '8869', 't']