It would be in between 17 and 27 because if you look at the line it will be on top of 21 and its in between them because if you look on the outer lines of the box those lines point on 17 and 27 and they are 8 pieces in between so between 17 and 27 it would be 8 and 10 so the answer would be c 17 and 27. I hope I could help!