You'll operate direct to Rio, then because you slept most of the way, you can continue onto Boners Aires - as long as certain very strict conditions are met:
Fack,
I'd be prepared to lay money that won't be the case. If it was, why aren't we doing DXB-SYD-AKL or DBX-MEL-CHR?
It'll be done like those trips- one crew augmenting both ways and doing the Buenos Aires shutlle, the other getting 48hrs off and operating both ways.