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: ['R', 'I', 'f', 'K', 'p', '8579', 'e', '1223', 'I', 'K', '8311', '2147', '4241', 'z', '6671', 'r']

SOLUTION: 31172

PROBLEM: ['z', 'c', 'E', 'Q', '1839', 'g', 'X', 'c', '291', 'c', 'w', 'e', '5957', 'X', '6471', 'A', '8359', 'y', '3611', '5417']

SOLUTION: 31945

PROBLEM: ['S', '439', 'N', 'Z', 'r', '3875', '9629', 'A', 'p', '7409', '8039', '3791', '5077', 'g', '7041', 'u', 'U', 'V']

SOLUTION:
45300