Possible Clues:

• "Can't argue with that!"
• "I can't argue with that"
• Job done, cabbie, but now I'm confused
• I don't know what the fare said on reaching destination?
• "I didn't think of that"
• I don't know opera lover's reason for living in New York
• We're so together, you texted, having turned 24? I don't know about that
• I am stumped what to say to taxi-driver on arrival
• One's acknowledgement to carrier on arrival: I'm stumped!
• ''I'm stumped!''