Prairie Restaurant is a famous old restaurant on the prairie, but it has some unwritten rules , if prairie restaurant sells both braised mutton and haggis soup on a certain day, it must also sell roast whole lamb; The restaurant never sells roast whole lamb on Sundays; ... People are familiar with these rules and take them for granted. In addition, we also know that Boss Wang only goes to eat at the Grassland Restaurant when he sells braised mutton.
If the Prairie Restaurant sells braised mutton on Sunday, it certainly does not sell haggis soup that day must also be true if this assertion is true.