In which of the following situations would the minimum efficient scale of operation provide little or no guidance regarding how many firms should serve the market to minimize production costs?

When the LARC (Long Run Average Cost) curve slopes downward over the relevant or material range of the output

Explanation:

LRAC stands for Long Run Average Cost, is that curve which represents the average cost, in the long period for producing a given or stated quantity of the output.

So, the one situation which will minimize the efficient scale of operation provide no guidance is when the LARC curve is downward sloping over the material range of the output. It states that the market should be served by a single firm in order to minimize the aggregate cost of the production.