Here's a puzzle about notes B1,aim2.8,P37,Para1.The paragragh is tell about the riskless arbitrage and I WAS 一头雾水。I can't understand:
1.Why "The hedge of market risk from a negative beta asset has a positive value"?
2.Why the forward price of oil,F,must be less than the expected future price of oil,E(Poil)?

The following is the original：

Oil Price With Positive Beta
In the second case,hedging oil price will decrease the firm's beta,but will also decrease the expected cash flow by the amount of the hedging costs.As we already discussed,for financial transactions that lower a firm's beta,efficient markets insure that the cost for bearing the systematic component of oil price risk avoided by hedging will be equal to the increase in the present value of a barrel of oil at the end of the period from the reduction in the firm's beta.

If this were not true,there will be a possibility for riskless arbitrage.A short forward position in oil would have a  negative beta(since a long position in oil has a positive beta).The hedge of market risk from a negative beta asset has a positive value.Entering into a short forward contract for oil must have a negative expected payoff,so the forward price of oil,F,must be less than the expected future price of oil,E(Poil).If the decrease in expected cash flow per share from selling oil forward at F does not just offset the decrease in beta,an opportunity for riskless arbitrage exists.
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