Morra

[RogerBear]

I am directing Donizetti's late comic opera RITA. In it, two men play a game of "morra" over the hand of a woman whom neither of them really wants. I understand that the game is played by shooting out from 1 to 5 fingers and simultaneously guessing the total number of fingers held up. As set in the opera, however, each player calls out three numbers. Here is the bidding:

A: 6, 5, 7
B: 5, 9, 7
winner A

A: 8, 5, 9
B: 6, 8, 7
winner B

A: 9, 7, 9, 5
B: 6, 8, 6, 2
winner B

It goes on, but I am lost already. HELP!