Answer: half a crown
Eliza: "Cheer up, captain. Buy a flower off a poor girl?"
Col. Pickering: "I'm sorry. I haven't any change."
Eliza: "Oh, I can change half a crown. Here, take this for tuppence."
Col. Pickering: "I told you, I'm awfully sorry. I haven't -- Oh, wait a minute. Oh, yes. Here's three ha'pence, if that's any use to you."