Question

why does the supply curve slope upwards

Answer 1

Firms need to sell their extra output at a higher price so that they can pay the higher marginal cost of production. Hence, decisions to supply are largely determined by the marginal cost of production. The supply curve slopes upward, reflecting the higher price needed to cover the higher marginal cost of production.

Answer 2

Firms need to sell their extra output at a higher price so that they can pay the higher marginal cost of production. Hence, decisions to supply are largely determined by the marginal cost of production. The supply curve slopes upward, reflecting the higher price needed to cover the higher marginal cost of production.