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.
['E', 'I', '3371', '4165', 'N', 'R', '5455', '7379', '7221', '5779', 'w', 'z', '2967', '1175', 'j', '3909', 'M', '9231', 'a', '629']