# Derivation of demand function

Hello. I'm graduate student in Japan.

This time, what I want to ask is how to solve the profit maximization problem using the image production function and derive the demand function.

This production function is a Cobb-Douglas production function, but it is also a CES type, and it is difficult for me to calculate.

Also, the paper states that the demand function has the same shape as a general monopolistic competition or an incomplete competition model.

So, the shape of the demand function is as follows.

$$Q_n(j)=[P_n(j)/P_n]^{-σ}*Q_n$$

where $$P_n$$ is final good price and $$P_n(j)$$ are intermediate goods (sector absorption) price