Equipment was purchased on January 1 for $64,500 with an estimated residual value of $4,500. The current year's Depreciation Expense is $6,000, calculated based on the straight-line basis, and the balance of the Accumulated Depreciation account at the end of the year is $42,000. The remaining useful life of the equipment is 1) 9 years. O2) 5 years.bg 3) 3 years. 4) 6 years