This is an interview problem from Glassdoor that I've been unable to solve.
You have all the clubs from a deck, 13 cards, and you can choose 2 from the deck and get paid their product, where all face cards are considered to be 0. You can pay $1 to reveal the difference of any two cards you choose, how much would you pay to play this game?
The answer given is "$79, because the 9 and 10 cards can be found in 11 steps", with no further explanation. Is this answer correct, and if so, how does one arrive at it? I tried diagramming out possible combinations of questions, but that method seems intractable.