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.
['2793', 'c', '7233', 'a', 'c', '841', 'I', '2299', '9755', '3673', '2823', '5651', '2207', 'n', 's', 'w', 'z', '4055', 'c']