Stage 9 - Q10 - 6 marks
19636
Challenge: Buy exactly \(7\frac{1}{2}\) L using 1.25 L packs at USD 2.60 and 0.75 L packs at USD 1.60. Packs are whole. Find the least possible cost and justify.
Hint
A cheap unit price is helpful, but the exact total volume must also be achievable.