The Suarez Trust generated distributable net income $($DNI$)$ this year of $$150,000,$ two$-$thirds of which was portfolio income, and the balance of which was exempt interest. Under the terms of the trust, Clara Suarez is to receive an annual income distribution of $$30,000.$ At the discretion of the trustee, additional distributions can be made to Clara, or to Clark Suarez III. This year, the trustee$$s distributions to Clara totaled $$60,000.$ Clark received $$90,000.$ How much of the trust$$s DNI is assigned to Clark?

a$.$ $$60,000$

b$.$ $$90,000$

c$.$ $$75,000$

d$.$ $$0,$ only first$-$tier distributions are subject to Federal income tax.