X's mom: Son, does economic theory explain why the price of a banana is lower in a flea market near 13hours as opposed to 8hs?
X: Yes, mom. It is because banana at 8h is a different commodity than banana at 13hs. Due to selective picking, what remains at 13hs is a worse kind of banana, less valuable. An umbrella in a rainy day costs much more to the passerby also because the change in the “state of nature” renders it a different product when weather is miserable.
X's mom: Oh, I see. So bananas are not all the same and that’s why they are priced different.
X's mom: Where did you learn this, son?
X: At Mas-collel, mom
X's mom: Is it a good read?
X: Definetely, and with a lot of intuitive discussions, mom. I will lend you mine.