On its December 31, 2017, balance sheet, Estes Co. reported its investment in trading securities, which had cost $500,000, at fair value of $475,000. At December 31, 2018, the fair value of the securities was $492,500. What should Estes report on its 2018 income statement as a result of the increase in fair value of the investments in 2018?

a. Realized gain of $17,500.

b. Unrealized gain of $17,500.

c. $0.

d. Unrealized loss of $7,500.