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You have to post a card to your sister. Since you’re not really familiar with that, see how far we can get. First try to pick up the CARD on the table. That’s a nice start. Then open the drawer, addressed to as postbox and see what’s inside. Take the giagantic PENCIL out and look what’s underneath: an ENVELOPE. Oh my…. Now what could we do with that?
Use the pencil in your inventory on the card in your inventory to get your name underneath. When you do that, you first open the card. Use the pencil again on the card to really scribble something between the lines. Use the card on the envelope to fill the envelope.
Now what more did we need to do? Ah! Use the pencil on the envelope so someone might see where the envelope needs to go to. Oh hell! The pencil broke. Let’s pretend we don’t have to send this card after all..
Game source: A copy of the game was found here  on the internet.