I had this exercise and I calculated the prices of the Arrow Securities, π1 = 0.5 and π2 = -0.2. I know that π2 is not arbitrage-free because -0.2 < 0, but I do not understand that how to interpret this result or what the arbitrage strategy is and what its cash-flows are, as it is asked in part b) of the exercise.
I hope someone can help!