【单选题】Caroline sharpens knives in her spare time for extra income. Buyers of her service are willing to pay $2.95 per knife for as many knives as Caroline is willing to sharpen. On a particular day, she is ...
【单选题】Sally sharpens knives in her spare time for extra income. Buyers of her service are willing to pay $2.50 per knife for as many knives as Sally is willing to sharpen. On a particular day, she is willin...