4. On January 1, 2014, Boone Company purchased a machine for $75,000 that had a 6-year life and a residual value of $6,000. After 3 years of use, on January 1, 2017, Boone Company paid $7,500 to improve the efficiency of the machine. The effect of the expenditure was to increase the productivity of the machine without increasing its remaining useful life or changing its residual value. Boone uses straight-line depreciation. (1) What account should be debited in recording the $7,500 expenditure? (2) Prepare the journal entry to record the depreciation expense for 2017. Date Account Titles Credit