Please help me with this. Where did they get 20 from? and what are the H & C formulas's they are using?

55. The stock price of Ajax Inc. is currently $105. The stock price a year from now will be either $130 or $90 with equal probabilities. The interest rate at which investors can borrow is 10%. Using the binomial OPM, the value of a call option with an exercise price of $110 and an expiration date one year from now should be wort_today. A. $11.59 B. $15.00 C. $20.00 D. $40.00 20-0-50 130-90 Buying the stock and borrowing the present value of $90 will give the same payoff as (1/.50) calls. 90 C. .5005-1.10)-11.59 1+.10