Puzzle ZDIN 

Workings

Hint
Who is in last place?

Answer
This cannot happen, you cannot overtake the person who is in last place, as there is no-one behind them!

Ovetaking = passing someone who is ahead on the same lap, this is a change of position, e.g. 4^th moves up to 3^rd.

Lapping = passing someone who is a full lap behind, this isn't a change of position, e.g. 4^th stays 4^th.