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.
['5779', 'b', '8069', '9831', '9295', 'z', 'g', '6935', 'M', 'z', 'N', 'K', 't', 'W', 'y', '1493', 'd', '1479']