A machine purchased on 1/1/21 for $24,000 and on which $14,400 of Accumulated Depreciation has been recorded through 12/31/23 was sold on 4/1/24. Straight-line depreciation was used. Salvage Value was zero. Asset life was 5 years. If the machine was sold for $16,000 cash, the journal entry to record this event would include a gain of:

a) $1,600 b) $8,400 c) $6,400 d) $7,600

The answer is D and I cannot figure out how. Please show work with answer.