Sum a list of numbers in Python for combinations

Question

I have 4 arrays, lets say like below:-

arr1 = [\'A\', \'B\',\'C\',\'D\',\'E\',\'F\',\'G\',\'H\',\'I\',\'J\']
arr2 = [\'k\',\'l\',\'M\',\'N\']
arr3 = [\'O\',\'P\',