"Because a firm's supply curve slopes upward, the long-run supply curve of an industry must also slope upward." Do you agree or disagree? Explain

What will be an ideal response?

Disagree. Even though a firm's supply curve slopes upward, the slope of the industry supply curve in the long run can be positive, negative or horizontal. An upward sloping industry supply curve reflects that an increase in industry output is accompanied by an increase in long-run average costs, while a downward sloping industry supply curve reflects a corresponding decrease in long-run average costs, and a horizontal industry supply curve reflects no change in long-run average costs.