When I work a logic problem without grumbling, you may be sure it is one that I can understand. These problems are not arranged in regular order, like the problems I am used to. No easy problem ever makes my head ache. I can’t understand problems that are not arranged in regular order, like those I am used to. I never grumble at a problem unless it gives me a headache.

Form valid conclusions in Problems 57–60 using all of the given statements. These problems were written by Charles Dodgson, better known as Lewis Carroll. You might wish to read the Historical Note and Example 5 in this section.