Gardner Corporation purchased a truck at the beginning of 2012 for $90,000. The truck is estimated to have a salvage value of $3,600 and a useful life of 120,000 miles. It was driven 18,000 miles in 2012 and 32,000 miles in 2013. What is the depreciation expense for 2012 :
A) $12,960
B) $13,500
C) $36,000
D) $21,600