This hand happened to me last night and I was wondering how everyone here would have played it.

$100NL on Party

I get dealt in CO...folds to me and I make it $4 to go. Only SB calls. Onlr read on SB is that he has been very passive after flop...I only have 60 hands with him though.

Flop comes
He checks to me I make it $8. He calls. At this point what should be my next move? Do I figure him for a higher pkt pair or something like KQ?

Turn comes ...It goes check check, b/c at this point I have no idea how to play my hand.

River is
He leads out for $15
Do I call the River bet and how would you all have played the hand?