1. A $648,000 property is depreciated for tax purposes by its owner with the straight-line depreciation method. The value of the building, y, after x months of use is given by y = 648,000 - 1800x dollars. After how many months will the value of the building be $387,000?

2. When an $810,000 building is depreciated for tax purposes (by the straight-line method), its value, y, after x months of use is given by y = 810,000 - 2250x. How many months will it be before the building is fully depreciated (that is, its value is $0)? How many years is this?