17. On January 1, 2015, Battle Company purchased a delivery truck for $252,000 with an estimated useful life of 140,000 miles and zero salvage value. The truck is being depreciated using the units-of-production method. The truck was driven 16,000 miles in 2015 and 20,000 miles in 2016. On January 1, 2017, an improvement was made to the truck that increased its total useful life to 160,000 miles and increased its salvage value to $1,400. The improvement cost $56,000. The firm reported $111,600 of accumulated depreciation on this truck at December 31, 2017. How many miles were driven in 2017? 9