Live game, river decision

[TomCowley]

Live game, 5/5, 8-handed. I have 180ish behind, the rest have me covered. I've hit a run of J3o and similar and haven't played a hand in 3 orbits.

CO is godawful and will pay off 3 half pot bets with bottom pair and draws to second pair with an A on board.

BTN has half a clue, but that's about it, definitely too loose, tends towards LAGgy.

SB is the definition of weak-tight and I own him regularly.

BB is tight and predicatable, and in position, I own him regularly.

Now for the hand:

3 players fold, and I'm in MP3 with A [img]/images/graemlins/heart.gif[/img]T [img]/images/graemlins/club.gif[/img]

I make it 25 to go, figuring I'm happy playing against anybody but the button.

CO Folds, BTN calls $25, SB folds, BB calls $25.

Flop K [img]/images/graemlins/spade.gif[/img] 7 [img]/images/graemlins/diamond.gif[/img]5 [img]/images/graemlins/diamond.gif[/img] (pot $80).

BB checks, I bet $50, BTN calls, BB folds.

Turn 9 [img]/images/graemlins/heart.gif[/img] (Pot $180)

I check, BTN checks behind.

River K [img]/images/graemlins/club.gif[/img] (pot $180)

I check, BTN bets $100. (I have under $110 left)

What do you do here and why?