Solve
-A Customer Paid $\$ 6.42$ In Sales Tax on a Set of Chairs That Cost

Solve.
-A customer paid $\$ 6.42$ in sales tax on a set of chairs that cost $\$ 321$ . What was the sales tax rate?

A) $2 \%$
B) $3 \%$
C) $4 \%$
D) $0.2 \%$