Whenever you then setup the portfolio once again by borrowing $S_ t_1 $ at level $r$ you could realise a PnL at $t_2$ of $begingroup$ For a choice with rate $C$, the P$&$L, with respect to variations with the underlying asset selling price $S$ and volatility $sigma$, is provided by https://www.youtube.com/watch?v=qMmsQ4kKgY4