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.
['T', '3603', 'u', '1643', '8911', '1433', 'g', '6431', '2863', '4807', 'j', '6525', '9997', '5871', '3703', '9995', '6429', '2255', '3527', 'y']