At the beginning of 1995, General Motor's pension funds were underfunded by $9.3 billion. Even though the company injected $10.4 billion during the year, at the end of 1995 the pension funds were still underfunded. Knowing that interest rates dropped during 1995, explain what must have happened. Explain how GM could have hedged its risk using (i) an immunization strategy and (ii) interest rate swaps.