Possible Clues:

• 'Likely story!'
• "Uh-huh, I bet" (In this answer, see letters 7-4)
• 'OK, I'll do it'
• "I bet!"
• 'Why not!'
• Skeptic's remark
• 'Uh-huh ... ri-i-i-ght'
• 'Now tell me another one'
• Sarcastic reply
• ''Whatever you say''