What is the underlying assumption when calculating the joint probabilities of the potential FX percentage change in a portfolio of foreign currencies from where the MNC wants to obtain financing? What are the main points that MNCs should be aware of and/or consider when they try to diversify away the financing risk of their global operations? What is the underlying assumption when calculating the joint probabilities of the potential FX percentage change in a portfolio of foreign currencies from where the MNC wants to obtain financing? What are the main points that MNCs should be aware of and/or consider when they try to diversify away the financing risk of their global operations