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.
['D', '1259', '8927', '3345', '553', '7209', '2507', 'l', 'o', '7317', '1227', '6749', 'S', '3171', 'I', '197', '9577', 'j', 'Q']