"Although the arbitrage explanation of swaps appears plausible at first glance, whether the gains are real or illusory depends on why the Quality Spread Differential [QSD] exists in the first place. (Wall and Pringle, 1989, p.60-61. Explain what Wall and Pringle mean by, the arbitrage explanation of swaps. How do Titmans (1992) asymmetric information model and Walls (1989) agency theoretic model explain why firms might use swaps? (30 marks)