A stock price is currently $30. During each two-month period for the next four months it is expected to increase by 8% or reduce by 10%. The risk-free interest rate is 5%. Use a two-step tree to calculate the value of a derivative that pays off max[(30-S),0]^2 where S is the stock price in four months? If the derivative is American-style, should it be exercised early?

Please explain your answer.