quiz number 20 From Stox book

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I realize that the book is geared to much higher stakes, than I play....so i was wondering if you were playing low stakes if the answer would be different.

You have QS6s and open raise from the button, loose passive in the big blind calls.

Flop comes 8d7s2d,you bet, bb calls. Turn is kh, you bet bb calls. River is Ac. Stox advocates betting the river, to get the BB to fold a better hand (only needs to fold 16% of time to be profitable). At the stakes I play, a loose passive will almost never fold a better hand on the river for one bet. If they have a pair they are calling down for one bet. Is this the proper play against a player who let's say folds to river bet 30% of the time?