Assume you have two stocks S$S$ and P$P$ so that at initial time t = 0$t = 0$: S_0 > P_0$S_0 > P_0$. You
You bought an option which pays off S_T - P_T$S_T - P_T$ as long as St > Pt though$S_t > P_t$ through the time 0 < t < T$0 < t < T$. What
What would be the price of such option be?
*I am looking for a non-arbitrage argument avoiding any specific distribution assumptions (log-normal, normal etc) if possible.