Suppose that we have three European calls with strikes $60,65,$ and $70$ and the same maturity $1$ month.

Their prices are $9\mathrm{.}00,7\mathrm{.}00,4\mathrm{.}00.$ Is it possible to do an arbitrage?

Suppose that current stock price is $100$$$.$ Its annualized volatility is $20\%$ and annualized return $10\%$ i$.$e$.$

we assume that the stock price follows $dxt=0\mathrm{.}1x{t}_t+0\mathrm{.}2x{t}_{tW}.$ Write the probability density function

for the stock in $1$ year. What is the mean and standard deviation of the terminal stock price? $($standard

deviation of price, not of return$)$