This is always negative, meaning cost per unit decreases as \( x \) increases? But the model \( C(x) = 5000 + 120x - 0.5x^2 \) is only positive for \( x < 250 \), and the current version increases linearly in cost, but quadratic loss? Actually, the cost function models *reducing* average cost? Let's reconsider. - Portal da Acústica