Back when Greek was a high-school subject, this sentence was an exam question.
British Columbia 1924
I wonder what the right answer was in those days.
You’re not alone, Joel! Where I found the potential optative was in Goodwin’s notes, where he uses δοίητε ἄν for the direct question. In the notes for the Mather & Hewitt edition, Mather uses δοῖτε ἄν. Doing a little digging, I came up with Smyth 758. S758a directly addresses the 2nd person pl. If I read it right, the shorter form appears in poetry, whereas both forms appear in prose.
I wonder what the right answer was in those days.
I think you would have been fine on the old exam—ancient Gk hasn’t changed that much in 100 years. εἰ δύναιντo/δύνανται/οἷοί τ’ εἶεν/οἷοί τ’ εἰσὶν/κτλ. or potent. opt. + ἄν should all be acceptable constructions. You can also use πότερον/πότερα for the indirect question.
It’s always a good idea to review the morphology of athematic verbs. Composition is the best way.