Error in Question 13

[d-alex-hughes]

The question text for problem 13 is a repeat of the question text for problem 12. The solution seems to exist for problem 13; but not the prompt.

As a short-run fix, I'll put a note in 13 that says, "This question is dead" but I'd like to hear from @sushovan4 how we should actually remove a question from the app in the most appropriate way.