Maximizing service of carousel storage

Jacobs et al. considered the problem on maximizing service of carousel storage and gave heuristics for the problem. Yeh improved the heuristics of Jacobs et al. We show that Yehʹs approach does not always lead to the optimal solution, and then give an algorithm finding the optimal solution by modifying Yehʹs approach. Our algorithm for the optimal solution is shown to be completed in polynomial time.