u(=upfactor) and d(=downfactor) are the following parameters:Consider a binomial model with one period and with parameters r(=interest rate) = 1/5, S_0 =
1, d = 3/4, u = 5/4. Compute the price of a European call option with strike price
K = 1, and find a replicating portfolio.
How can I determine the price at S_0 ?