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.
['4071', '4295', '1917', '1291', 'k', '3389', 'T', '45', '6701', 's', 'X', '5579', 'X', '3591', '3127', 'M', 'd', '3679', 'Z']