Can you do a single run on the last day of the year?

Sure, but to be able to fulfill all the year's orders (expected to total 12,000) a single run would have to be on the first day of the year. Setup cost = 300. Now we have 12,000 components to store. If the orders come in steadily, the last component will be sold on the last day of the year. Average quantity stored over the whole year will be 6,000 components. So storage will cost 24,000. Total cost 24,300.

Doing one run each month (quantity = 1,000 a month) would entail setup costs of 3,600. And storage costs of 4 * average storage of 500 components = 2,000. For a total cost of 5,600.

All according to the given model, of course, but I think this is the general idea.