B12. (Net advantage of refunding) IBM has $150 million of 10% sinking-fund debentures out- standing. The issue amortizes in equal annual amounts at the ends of years 10, 11, and 12. The firm can call the bonds at 103%. Its new issue rate is 8% for 10-year debt, 8.5% for 11-year debt, and 9% for 12-year debt. Its marginal income tax rate is 40%. Which sinking-fund amounts should the firm call?