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.
['191', 'R', 'Q', '7809', '4851', 'b', 'e', 'H', 'E', 'I', 'r', 'A', 'g', 'e', 'g', 'I', 'j', 'f', '7287']