Consider an American call option when the stock price is $19, the exercise price is $21, the time to maturity is 6 months, the volatility is 25% per annum, and the risk-free interest rate is 10% per annum. Two equal dividends are expected during the life of the option with ex-dividend dates at the end of 2 months and 5 months. Assume the dividends are 45 cents. How high can the dividends be without the American option being worth more than the corresponding European option?