This course considers the behaviour of firms in a market economy. It has two parts. One - the basic theory part - considers how firms behave under different market structures. The other part is policy-oriented. It applies tools from the basic theory part to everyday problems and scenarios and tries to assess market efficiency and effects of possible intervention by the government or regulatory agencies. The two parts proceed simultaneously. Real-life problems or scenarios are introduced and while discussing them the required theory is developed. Students must be able to take derivatives and solve optimization problems and think critically in a logical manner.