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.
['g', 'I', 'S', 'y', '1175', 'e', '6187', 'P', 'j', 'f', '8303', '99', 'O', 'C', '6795', 'W', '6129', '6237', '8029']