Please help me solve this question. Thank you.
Let the Geometric Brownian motion be: $$ \frac{\Delta S}{S} = \mu \Delta t + \sigma \epsilon \sqrt{\Delta t} $$
$\Delta S$ = change in stock price (s)
$\mu$ = expected rate of return
$\sigma$ = volatility of shock
$epsilon$ has standard normal N(0,1) distribution
$\sigma \epsilon \sqrt{\Delta t}$ = stochastic companion
i) Derive the Ito process with a drift for the above ii) Given that the option price at time $t$ is $f(s,t)$, derive the process with Ito's lemma. Give an example.