On its December $31,2020,$ balance sheet, Trump Company reported its investment in equity securities$,$ which had cost $$600,000,$ at fair value of $$560,000.$ At December $31,2021,$ the fair value of the securities was $$585,000.$ What should Trump report on its $2021$ income statement as a result of the increase in fair value of the investments in $2021?$

a$.$ $$0.$

b$.$ Unrealized loss of $$15,000.$

c$.$ Realized gain of $$25,000.$

d$.$ Unrealized gain of $$25,000.$