Gilly Construction trades in an old tractor for a new tractor, receiving a $28,000 trade-in allowance and paying the remaining $84,000 in cash. The old tractor had cost $75,000, and straight-line accumulated depreciation of $40,625 had been recorded to date under the assumption that it would last eight years and have a $10,000 salvage value. Answer the following questions assuming the exchange has commercial substance. 1. What is the book value of the old tractor at the time of exchange