A) Amount of Suta tax the company must pay to Tennessee on Herb Porter's wages.
9,900*3.2%= 316.80
If only $2800 of wages were paid in Tennessee, why would you have to pay SUTA on the entire $9900? It's also only paid on the first $7000 of wages, so nowhere would there be any tax beyond that $7000 limit, TN or SC either one.
B) Amount of SUTA tax the company must pay to South Carolina on Porter wages.
7100*3.8=269.80
That too is over the $7000 limit. This is also a little tricker because you would have to know SC's rules. Every state is different. SC might make the company "start over" on that $7000. That is, the $2800 from TN being irrelevant and not counting, and only counting the amount paid in SC. Or... they might consider the $2800 paid in TN as fulfilling the first $2800 of the $7000 limit, in which case there'd be tax on the $4200 difference.
You aren't getting the concept of the ceiling. That means the first $7000 per year of each employee's income is taxable for unemployment. No wages beyond $7000 are taxed - it stops.