Layne thinks that the probability of a catastrophic climatic event 65 years from now is low. His discount rate is 2.70%. Chris think that the probability of a catastrophic climatic event 65 years from now is 4.30%. The cost of preventing the catastrophic event is $40 billion now. The damages from the catastrophic event are $110 billion 65 years from now. The difference between Layne's and Chris's present value of net benefits of preventing the catastrophe is __________ billion dollars.