Centronix Corporation purchased new equipment with an estimated useful life of five years. The cost of the equipment was $200,000, and the residual (salvage) value was estimated to be $25,000. In purchasing the new equipment, an old machine was traded in that had an original cost of $180,000 and had been depreciated at the rate of $18,000 a year. The trade-in allowance was $21,000, and accumulated depreciation amounted to $144,000 at the time of the exchange. What should be the cost basis of the new equipment for tax depreciation purposes? (a) $200,000 (b) $215,000 (c) $175,000 (d) $190,000