Jeffrey Dean, a Master's Degree candidate at North State Central University, was awarded a $$15,000$ scholarship from North State Central in the current year. During the current year, he paid the following expenses:

Tuition $$12,000$

Books $1,000$

Fees $500$

Room and Board $1,500$

In addition, he received $$6,000$ for teaching two undergraduate accounting courses. What amount must be included in Dean's gross income?

a$.$ $$0$

b$.$ $$6,000$

c$.$ $$7,500$

d$.$ $$21,000$