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.
['2679', 'd', '1145', 'h', 'i', '4313', '8955', 'F', 'U', 'U', '7341', '979', '3257', 'S', '6413', 'H', '2987', 't', 'I', '6041']