Final answer:
The lowest acceptable transfer price for the selling division is the market price.
Step-by-step explanation:
The lowest acceptable transfer price for the selling division in the scenario where there is unsatisfied demand from outside customers is the market price.
The selling division wants to maximize its own profit, so it would prefer to sell the product at the market price, which is determined by the demand and supply in the market. By selling at the market price, the selling division can ensure that it is not losing potential revenue or customers to competitors.