I just unlocked a document with the following example but I can't figure out where the $136,320 amount is coming from. Please I need in detail how it reaches that number.

A building is acquired on 15 June 1991 at a cost of $85 000. Legal fees associated with the purchase amounted to $2 000. Capital renovations were carried out in February 1995 at a cost of $27 000. In June 2016 the building is valued for sale, valuers' fees amounting to $2 000. The building is disposed of in October 2016 for consideration of $150 000. Agents fees on the sale are $4 000.

Capital proceeds = $150 000

Capital gain using indexed cost base = $150 000 - $136 320 = $ 13 680

Capital gain using cost base = $150 000 -$ 120 000 = $ 30 000

Assessable capital gain = $30 000 * 50% (CGT discount) = $ 15 000