Solving the Genie's Riddle

The Genie first encountered within the Circus Tent in Waukeen's Promenade addresses the party with a question, which is a puzzle or a riddle of sorts. The party may not pass unless the riddle is at least attempted to be solved. Select an answer from the multiple choices displayed.
Paraphrased for brevity, the genie says:
The correct answer is: "The Prince is 30, and the Princess is 40". (Party members share )
If the incorrect answer is given, the genie mocks you and gives a second question:
The correct answer is: "Nothing". (Party members share )
Solving the genie's puzzle (or killing it) is needed in order to advance across the bridge. The riddle is a variation on the Puzzle of "How old was Mary?" from Sam Loyd's Cyclopedia of Puzzles.