What is the net book value of debt? Show how you arrived to that number in detail.

Following is the debt footnote from the NMG Inc. 2013 annual report (In millions): Real properties with an aggregate book value of $64 million were pledged as collateral at December 31, 2013 for secured debt. Amount includes $100 million of notes issued in 1997 that may be put at the option of the holder on the 20th anniversary of the issue at par value. None of these notes are currently puttable. Interest rate listed in the above table is weighted-average interest rate