The current price of a non-dividend-paying biotech stock is $140 with a volatility of 25%. The risk-free rate is 4%. For a three-month time step:

a) What is the percentage up movement?

b) What is the percentage down movement?

c) What is the probability of an up movement in a risk-neutral world?

d) What is the probability of a down movement in a risk-neutral world? Use a two-step tree to value a six-month European call option and a six-month European put option. In both cases the strike price is $150.

Please explain your answer.