The next $4$ questions refer to the following situation:

In the provided blank, insert the letter that corresponds to the correct answer. For example, if the correct answer is $"$a$)1\mathrm{.}990",$ insert only $"$a$"$ as the correct answer.

A firm is about to undertake the manufacture of a product, and it is weighing the process configuration options. There are two intermittent processes under consideration, as well as a repetitive focus. The smaller intermittent process has fixed costs of $$3,000$ per month and variable costs of $$10$ per unit. The larger intermittent process has fixed costs of $$12,000$ per month and variable costs of $$2$ per unit. A repetitive focus plant has fixed costs of $$50,000$ per month and variable costs of $$1$ per unit.