Hi,

I am working on below challenge

http://codingbat.com/prob/p180365
The "key" array is an array containing the correct answers to an exam, like {"a", "a", "b", "b"}. the "answers" array contains a student's answers, with "?" representing a question left blank. The two arrays are not empty and are the same length. Return the score for this array of answers, giving +4 for each correct answer, -1 for each incorrect answer, and +0 for each blank answer.

i was not clear on above description.

i was not clear how below result is 6 etc. please advise

scoreUp(["a", "a", "b", "b"], ["a", "c", "b", "c"]) → 6

scoreUp(["a", "a", "b", "b"], ["a", "a", "b", "c"]) → 11

scoreUp(["a", "a", "b", "b"], ["a", "a", "b", "b"]) → 16