ITM has $150 million of 10% sinking-fund debentures outstanding.

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%.

Post the net advantage of refunding for each one. Which sinking-fund amounts should the firm call?