Using q₁ = 20 − 2P and q₂ = 30 − 3P, what is market demand at P = 4?

Explanation

1. 01

   q₁ = 20 − 8 = 12; q₂ = 30 − 12 = 18.

2. 02

   Market demand = 12 + 18 = 30. Check: 50 − 5 × 4 = 30.