On December 31, Strike Company sold one of its batting cages for $20,000. The equipment had an initial cost of $310,000 and had accumulated depreciation of $260,000. Depreciation has been recorded up to the end of the year. What is the amount of the gain or loss on this transaction?

a.loss of $20,000

b.gain of $20,000

c.loss of $30,000

d.gain of $30,000