Proficiency(Technique) to receive a Reward

One Day, A Lady Lost her purse in a very busy department store.

She searched everywhere she had visited, but just couldn't find it.

Finally, a little Boy approached her and asked, "Ma'am, is this your purse?"

Jubilantly, she grabbed the purse and cried, "Yes! Yes, it is! Thank you,
Thank you so much!"

Then she looked inside the purse and was suddenly dazzled(confused).

"But how strange... when I lost it, I had only 'A Hundred Dollar Note',
but now, I have Five Twenties!"

The Boy replied, "That's because the last time I returned a lady's purse,
She didn't have any change for a reward!".