In Muskegon, Michigan, there are three very popular supermarkets: Meijer, Aldi, and Wal$-$Mart. While Meijer remains open twenty$-$four hours a day, Aldi and Wal$-$Mart close at $9$ pm$.$ Which of the following statements is true?

WinCo can ignore the pricing decisions of the other two supermarkets.

WinCo has a monopoly at midnight but not during the day.

WinCo is a monopoly all day because it produces a service that has no close substitutes.

WinCo probably has a higher markup to compensate for its higher cost of production.