(Reef Cairns isn't a spell.)
Reef Cairns enters the battlefield tapped.
, : You may put a land card from your hand onto the battlefield.
: Add or to your mana pool.
Sacrifice Reef Cairns: Add or to your mana pool.
, 
: You may put a land card from your hand onto the battlefield.: Add 
or 
to your mana pool. or to your mana pool.
