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.

['8313', 'x', '915', '4929', '4413', '4845', '7585', '2311', '9415', '755', '4919', '1871', '8977', '4521', 'J', '4735', '7203', 'b']
75707