प्रो. नाइट ने अपनी किस पुस्तक में लाभ के अनिश्चितता सिद्धांत का प्रतिपादन किया?

According to Frank Knight, pure profit arises as a reward for:

What do you call the profits earned by a business firm over and above the opportunity cost of the factor inputs?

According to Frank Knight's theory of profit, uninsurable risk (uncertainty) arises due to which type of changes?