Brash tease! Pedestrian persuaded to have a THREESOME!

Ok, I didn't expect that. I had a bet with my girlfriend that she wouldn't dare ask the first person we met if he wanted to FUCK both of us. I never thought she would do that easily :P Of course the guy said yes straight away. He probably noticed that we were pretty horny and when do you get such a chance to fuck such horny girls like that ;) How would you have decided?