4. (10 points) Suppose that the price of a stock today is at $30. For a strike price of $25 a 6-month European call option on that stock is quoted with a price of $12, and a 6-month European put option on the same stock is quoted at $4. Assume that the risk-free interest rate is 1% per annum (with continuous compounding). (a) Does the put-call parity hold? (b) Is there an arbitrage opportunity? If yes, carefully explain how the arbitrage strategy would look like. Provide all necessary details of the strategy and the arbitrage gain