The current price of NLT stock is $20 and the stock price will increase by 10% or decline by 5% at the end of each month. NLT pays no dividends. The continuous risk-free interest rate is 4% p.a., which will remain constant forever. Construct a two-step binomial tree to describe the price evolvement of the stock and calculate the price of a 2-month American call option on NLT stock with a strike price of $22.