A portfolio contains a long position in a call option with strike price $25, a short position in a call option with strike price $35, a long position in a put option with strike price $35, a short position in a put option with strike price $25. The options are European style on the same underlying asset and have the same expiration time six months from now. Find a formula for the value of the portfolio, V (S, t). How much would you pay for this portfolio if the interest rate is 5%?