Suppose there are two consumers in the market for a good and their demand functions are as follows: for any price less than or equal to 20, and at any price greater than 20. for any price less than or equal to 15 and at any price greater than 15. Find out the market demand function.
The market demand function is:
For price less than or equal to 15: D(p) = 50 - 3p
For price greater than 15 and less than or equal to 20: D(p) = 20 - p
For price greater than 20: D(p) = 0
Explanation
This question tests the concept of horizontal summation of individual demand curves to derive market demand. The key insight is that consumers exit the market at different price thresholds. Consumer 2 exits when price exceeds 15, while Consumer 1 exits when price exceeds 20. Therefore, we need to consider three price ranges: when both consumers are active (p 15), when only Consumer 1 is active (15 < p 20), and when neither is active (p > 20).
Solution Steps
Step 1: Identify the price ranges where each consumer is active. Consumer 1 is active for p 20. Consumer 2 is active for p 15.
Step 2: For p 15, both consumers are active. Market demand D(p) = d₁(p) + d₂(p) = (20 - p) + (30 - 2p) = 50 - 3p.
Step 3: For 15 < p 20, only Consumer 1 is active. Market demand D(p) = d₁(p) + 0 = 20 - p.
Step 4: For p > 20, neither consumer is active. Market demand D(p) = 0.