First post! hey guys. got caught up in multitabling and got lost in this hand. was really confused by the river, hopefully you all can help with the line i chose

I have  in the BB

CO min opens to $1, SB and I flat

(POT $3)

 

SB checks, I bet $2.75, CO calls and SB calls

(POT $11.25)

 

SB checks, I bet $5.55, CO raises to $15.35, SB folds and I call

(POT $42)

 

I check and CO bets $ 30, hero??

CO is virtually unknown. 30 hands on him and he's playing 17/10. dont know what is standard open is. thoughts on all streets please. ty!