June Whipple, a sporting goods retailer, purchased backpacks from a supplier for $$7,245.$ The supplier offers a $5\%$ discount if the invoice is paid within $10$ days; if not paid within $10$ days, the full amount must be paid within $30$ days of the invoice date. Use the formula $R=\frac{\text{I}}{PT}$ to find the annual rate June, in effect, is paying the supplier if she fails to pay the invoice at the end of the discount period. Hint: June is$,$ in effect, borrowing the net amount $($amount after deducting the discount$)$ for $20$ days and must pay the difference as interest.