2. (a) If D is the present value of all future dividends on a dividend paying stock, use replicating portfolios to derive a put-call parity formula for a European option on the stock. (b) A European call option and a put option on a stock both have a strike price of $20 and and expiration date in three months. Both sell for $3. The risk-free interest rate is 10% per annum, the current stock price is $19, and a $1 dividend is expected in one month. Identify an arbitrage strategy