Whats the price of a European Put Option with a strike of $75 and expiring in 6 months on a stock which is trading at $100 today? Assume a risk-free interest rate of 5% and a stock volatility of 20% per annum. What should be the price of a European Call Option with the same paramenters?

You look in the market and see that the quoted price is 25. What should be the implied volatility using that quoted option? What should be the quoted price of the matching European Call Option?