TASK DEFINITION: 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.
PROBLEM: ['507', 'P', '9697', 'u', '5057']

SOLUTION: 15261

PROBLEM: ['4601', '6021', '3005', 'I', 'f', '4631', 'Q', 'd', '8041', 'D', '8067', '7383', '757', 't', 'd', 'n', '2275', 'p', 'm', '6021']

SOLUTION: 50802

PROBLEM: ['z', 'B', '29', '3959']

SOLUTION:
3988