A firm offer to sell up to 10,000 tubes of toothpaste at $1.00 per tube remains open for 45 days. After 45 days, the price increases to $1.10. The retailer orders 6,000 within 45 days and 4,000 after expiry. What price may the supplier charge for the 4,000 tubes ordered after expiry?

• A. A $10,000
• B. B $10,400
• C. C $11,000
• D. D $11,400

Answer: (B)

Firm offers create a binding price for the time stated, but only for the period. Here, the offer fixes the price at $1.00 per tube for up to 10,000 tubes during 45 days. The buyer buys 6,000 within that window, forming a contract at $1.00 for those tubes. After the 45 days, the offer lapses for new quantities, so the supplier may charge the going price at that time, which is $1.10 per tube for the 4,000 tubes ordered after expiry. So the 4,000 would cost 4,000 × 1.10 = 4,400, and the total for all 10,000 tubes would be 6,000 at $1.00 plus 4,400 at $1.10, totaling $10,400. This matches the correct answer.