I need to figure out the cost of an asset using Double Declining Balance method with this given information: Residual value = $20,000, Service life = 5, Depreciation for year 2 = $24,000.

Working backwards, I have already figured out that the net book value of the asset for year 2 is $60,000.(x * 40% = 24,000; 24,000/.40 = $60,000)

I actually know the answer, from research, is $100,000, but I do not know how I would get that answer with this information. Please help.