Consider a single period binomial model where the stock has an initial price of $100 and can go up 15% or down 5%. The price of the European call option on this stock with strike price $115 and maturity after one period is $0.12. What should be the price of the risk-free security that pays $1 after one period regardless of how the stock price develops? Assume that maturity is T = 1. (This is the same as disking about the discount factor that makes the market arbitrage-free. Why is that?)