The forward linked spot and interest rate.
$F = S(t)e^{r(T-t)}$
$F = S(t)e^{(r+s-c)(T-t)}$
$F = S(t)e^{(r-r_f)(T-t)}$
$F = S(t)e^{(r-q)(T-t)}$
As it stands, this profit diagram takes no account of the time value of money. The premium is paid up front but the payoff, if any, is only received at expiry. To be consistent one should either discount the payoff by multiplying by e −r(T−t) to value everything at the present, or multiply the premium by e r(T−t) to value all cashflows at expiry.
The most important: Spot amd Expiry <------ variables
interest rate and strike are just parameters <------ parameters
Other parameters: dividend, fx interest and volatility!
Hedging and No arbitrage
Option payoffs can be replicated by stocks and cash.Any two points on the straight lines can be used to get us to any other point. So, we can get a risk-free investment using the option and the stock, and this is hedging. And, the stock can be replicated by cash and the option.
The practical implication of complete markets is that options are hedgeable and can therefore be priced without any need to know probabilities.