Jotun Grunt and cumulative upkeep

[Polynomial P]

Lets say I have a Jotun Grunt in play with 3 age counters on it. My opponent has 4 cards in his graveyard and I have none. Can I put his four cards on the bottom of his library and then sac the grunt?

Basically, can I pay as much as possible (similar to when Phyrexian Dreadanout comes into play, i have to sac creatures even if their total power does not equal twelve). Thanks.

[parallax]

No, you must pay the full cumulative upkeep. You could pay it from separate graveyards if you had two cards in your own 'yard.