Consider an American call option on a dividend-paying stock. The stock price is $40, the strike price is $45. The volatility is 25% per annum. The time to maturity of the option is six months. The risk-free interest rate is 3% per annum. Two equal dividends of 20 cents are expected during the life of the option, with ex-dividend dates at the end of one month and four months. Use Blacks approximation to value the option.