Show that rising portion of MC curve is the supply curve itself.

Rising portion of MC curve is the supply curve itself. How? Recall that the basis of law of supply or supply curve is increasing marginal cost. In the adjoining Fig. 3.10, MC curve is U-shaped and Pi is the price line under perfect competition. At price P₁, the price line cuts MC curve at two points — at and Qb₁, i.e., it satisfies profit maximising condition P = MC at two places. But total profit at output level of Q^b1 is higher. Therefore at price P₁, the firm produces the amount Qb₁, It means that if price is OP₁, the firm will supply OQb₁ level of output. Similarly if price is OP₂, the firm would supply (produce) OQ₂ level of output and at price OP₃, it would supply (produce) OQ₃level of output; and so on. We see clearly that all price-output combinations are simply the points on the rising portion of MC curve. Hence it is concluded that the rising portion of MC curve is the supply curve itself.