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: ['291', 'R', 'N', '983', '2879', 'C', '3797', '4837', '793', '5489', 'k', '535', 'L', '3605', 's', '3701', 'U', '4399', '2489', '4739']

SOLUTION: 38537

PROBLEM: ['t', 'Q', '5189', 'g', 'c', '4685', '5309', 'W', '6729', '2843']

SOLUTION: 24755

PROBLEM: ['u', '5097', '225', 'R', '7003', '1727', '1861', '9645', 'D', 'I']

SOLUTION:
25558