I shall indicate what the difference between new and old economic theories below: In old economic theories, they may include: Scarcity means that the condition in which our wants and greates than our limited resources. So, we must make choices on how we will use resources. Hence, economic-social concerned with the efficient use of limited resources to achieve maximum satisfaction of economic wants; micro-economic studies such as individuals, firms and industries ( competitive markets, labour markets, personal decision making etc.) Otherwise, macro-economics studies the large economy as a whole or in its national economic growth. Government how spends, inflation, unemployment etc. Marginal analysis involves making decisions based on the additional benefits vs. the additional cost.⦁Old economic theory ⦁production possibilities curveEveryone acts rationally by comapring the marginal costs and marginal benefits of every choice. For example, if you decide to go to college, the opportunity cost of going to college may include work to earn money, production possibilities have four assumptions: Only two goods can be produced, full employment of resources, fixed technology, resources. For example, when one firm produces two products . One is pizza food, another is robots. It produces many robots, then it will produces less pizzas. If it hopes to involve to produce pizzas, but it won't reduce to produce robots. It must need to improve technology in order to improvements in pizza ovens, but robots producing number won't be reduced . If the country has mad cow disease kills 85% of cows, then it will influence the demand for pizza decrease. Then, it may avoid to improve technology to produce many pizza, it can concentrate on applying technology to produce new robot making technology. In the production possibiliteies curve and efficiency refers this firm can have productive efficiency when robots are being produced in the least costly way, due to pizzas produced number is reduced, this is any point on the production possibilities curve as well as allocative efficiency, when this firm's robots being produced are the ones most desired by society. This optimal point on depends on the robotic products desires of society.So, the less demand to pizzas, it will influence it applies less technology to produce pizzas, but more technology to be improved to concentrate on producing robotic products.⦁Specialization of trade theorySpecialization of trade explains one country can earn comparative advanage when the producer will be lowest opportunity cost to produce. So, countries should trade if they have a relatively lower. For example, US specializes and makes only wheat. Brazil makes only sugar. So, US can export wheat and Brazil can export sugar to earn comparative advantages . When there two countries only concentrate or producing on kind of food in order to earn specialization trade advantages. Free market means little government involvement in the economy, ( laissez faire), individuals own resources and the opportunity to make profit gives people incentive to produce items efficiently, wide variety of goods available to consumers and competition and self-interest work together to regulate the economy keep computers and only one company is making them, other making computers to earn profit.