Rock Company purchased manufacturing equipment for $500,000 on April 1, 2012. The estimated salvage value is $50,000, and the estimated total useful life is 5 years. The straight-line method is used for depreciation. What is the gain or loss on sale if the asset was sold for $215,000 on May 1, 2015?

a. $75,000 gain

b. $15,000 gain

c. $ 7,500 gain

d. $ 7,500 loss