Fun at school

I'm in class today teaching, and we're doing a round of "do you have a sister?" I get to little Abby, who is about 10 years old, and has bright red glasses, a squeaky little voice, and these bouncy pigtails. Basically she's the cutest thing ever.

I say "Abby, do you have a sister?" And she answers "Yes, I do" and I ask "How old is she?" and without hesitating with a dead straight face she says "She is $15 dollars."

Honest mistake, I know, but so cute!