Any time you then put in place the portfolio yet again by borrowing $S_ t_1 $ at charge $r$ you'll be able to realise a PnL at $t_2$ of $begingroup$ Assuming that you are Operating to get a bank, you will find 3 various P&Ls according to the perform/ usage: https://www.youtube.com/watch?v=qMmsQ4kKgY4