Net book value vs. amount reported on balance sheet

I’m working on a problem that asks you to find the percent of other intangible assets pledged as collatteral, but I’m having trouble figuring out why the denominator uses the value from the balance sheet as opposed to the net book value from notes to the financial statements.

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Please post a page number; is this the 2015 curriculum?

It’s the second to last example in reading #30. The bookshelf software that the CFAI book uses doesn’t state the actual page the question is on. However, in the 2012 book (I have the physical copy of that) the identical question can be found on page 474.

The footnotes are explaining the net book value of the pledged assets, not the total net book value; the total net value is on the balance sheet.