Q.A firm under perfect competition sells its output at the market price of ₹10 per unit. Its total cost is $TC = Q^{2} + 2Q + 25$. Find the profit-maximising output and the amount of profit.

In perfect competition, price is fixed by the interaction of market demand and market supply at the point where they are equal (equilibrium price); individual firms accept this price as given and are price-takers.

Perfect competition is a market with a very large number of buyers and sellers, a homogeneous product, free entry and exit, perfect knowledge, and perfect mobility of factors. Because each firm supplies only a tiny part of total output, no single firm can influence the price — the price is set for the whole market and each firm is a price-taker.

Role of demand and supply: The market price is determined by the interaction of the total market demand and the total market supply of the commodity.

• The market demand curve slopes downward (more is demanded at lower prices, by the law of demand).
• The market supply curve slopes upward (more is supplied at higher prices, by the law of supply).

Equilibrium price: The price settles at the level where quantity demanded equals quantity supplied — where the demand and supply curves intersect. This is the equilibrium (market) price, and the corresponding quantity is the equilibrium quantity.

• If price is above equilibrium, supply exceeds demand (a surplus). Competition among sellers pushes the price down toward equilibrium.
• If price is below equilibrium, demand exceeds supply (a shortage). Competition among buyers pushes the price up toward equilibrium.

Only at the equilibrium price is there no tendency for price to change, because the plans of buyers and sellers exactly match.

Role of time (Marshall's analysis): The way demand and supply determine price depends on the time available to adjust supply:

• Market period (very short run) — supply is fixed (perishable goods), so demand mainly determines price.
• Short period — supply can be varied only by changing variable factors, so both demand and supply influence price. …

Under perfect competition, price is fixed by the intersection of market demand and market supply; the firm is a price-taker.

This 8-mark item is a core price-determination topic in CHSE Odisha +2 Business Economics (aligned with the NCERT/CBSE curriculum).

Features of perfect competition. A very large number of buyers and sellers, a homogeneous product, free entry and exit, perfect knowledge, perfect factor mobility, and no transport cost. Because of these, a single uniform price rules in the market, and an individual firm is a price-taker facing a horizontal (perfectly elastic) demand curve at that price, so for the firm Price = AR = MR.

Determination of market price. The market (industry) price is settled by the forces of total demand and total supply:

• The market demand curve slopes downward (buyers buy more at lower prices).
• The market supply curve slopes upward (sellers supply more at higher prices).
• Equilibrium price is where the two curves intersect — the price at which quantity demanded equals quantity supplied. At any higher price there is excess supply, pushing price down; at any lower price there is excess demand, pulling price up. Only at the equilibrium price is the market cleared.

Illustration.

Here the equilibrium price is Rs. 4, where demand = supply = 200 units.

The firm's position (time element — Marshall). Once the market fixes the price, each firm takes it as given and chooses the output at which it earns maximum profit, i.e. where MC = MR (= price) and MC is rising. …