 In this section, I will explain the concept of arbitrage pricing model. So, we use different types of models to price a financial instrument. We have earlier discussed the concept of capital asset pricing model, which is also known as CAPM. We also use it to determine the price of any financial instrument. There is another model which was developed by Stephen Ross in 1970s, which explains how we can determine the price of any financial instrument. And this particular model is altogether different from CAPM. In CAPM, we take the risk-free return of market index and the value of market index. But here, we account for macroeconomic factors. And we determine how these systematic factors can contribute to fluctuations in the overall prices of that particular asset, which we want to determine the price of. So, basically, we account for these factors of asset or portfolio, which we account for systematic factors or say, we assess them in this model. Basically, this theory of asset pricing model is defined as if you have a portfolio which is well diversified, in which you have included assets to construct the portfolio, the objective of the investor is to maximize the expected returns by considering these different types of factors and diversifies it from that perspective. And in this, we consider the value of the asset, the key elements are some of the systematic factors, which are macroeconomic factors. Those factors are some of the indicators of the overall economy. And in APT, we are applying the basic assumption that if any financial instrument is being purchased in any country, the value of that is significant from the macroeconomic factors of that economy. So, the macroeconomic factors we consider in this model, they include inflation. What is the value? They also include the overall industrial production. How much is that? We account for the risk premiums in that. And we use one more important thing in this. That is the term structure of the interest rate. So, these are the four key systematic factors and macroeconomic factors that are accounted for in APT to calculate or to determine the price of a financial instrument. So, in APT, we consider these particular factors and see how these factors' value changes can influence our price. How can we, by considering the values of these particular macroeconomic variables, how can the value of a certain specific financial instrument be determined?