Final answer:
Barney's gross income includes $6,300 from his part-time teaching assistant job ($700 per month for 9 months) and a $1,500 research grant, totaling $7,800. The tuition waiver does not contribute towards his taxable gross income.
Step-by-step explanation:
The gross income for Barney, who is both a graduate student and teaching assistant at State University, comprises his monthly salary and the research grant he receives. His tuition waiver is not counted as income for tax purposes. Therefore, Barney's gross income is calculated by multiplying his monthly salary of $700 by 9 months, giving us $6,300 from his teaching assistant role. Barney's gross income can be calculated by adding up all of his sources of income. He is paid $700 per month for nine months as a teaching assistant, so his total income from this job is $700 * 9 = $6300. He also receives a $1500 research grant. In addition, his $5000 tuition is waived by the university. Therefore, Barney's total gross income is $6300 + $1500 + $5000 = $12,800.
Then, we add the $1,500 research grant that Barney receives. This totals a gross income of $7,800 for the year. B. $6,300 for salary and $1,500 for the research grant, summing up to $7,800 in gross income.