4. An American put option to sell a British pound for dollars has a strike price of $1.5 and a time to maturity of 1 year. The volatility of the pound/dollor exchange rate is 15% per annum, the dollar interest rate is 6%, the British pound interest rate is 7%, per annum, and the current exchange rate is 1.52 . Use a three-step binomial tree to value the option