Suppose that an asset price evolves according to the binomial model. For simplicity, suppose that the risk-free interest rate is zero and delta t is 1. Suppose that under the binomial model, the asset price can either go up by a factor of 2 or down by a factor of 0.5 at each time step. If the current asset price is $100, what are the possible asset prices after two time steps?
a) $50 and $200
b) $25 and $400
c) $100 and $200
d) $50 and $400