Assume a non$-$dividend paying stock, an American call option and a European put

option on the stock with the same strike price K$.$ The maturity of the options is one

year. The stock price is $31,$ the strike price $30,$ the risk$-$free interest rate is $10\%$ per

annum $($continuously compounded$),$ the price of the call is $3$ and the price of the

put $1.$ The stock can either go up by $20\%$ or down by $20\%.$ What would you do to

make money? Which prices exclude arbitrage? I know it need to use put$-$call parity formula, I have calculated these equation price but don't know how to argitrage and which price exclude arbitrage.