Suppose a perfectly competitive firm's total cost of production (TC) is:

TC(q) = q^3 -10q^2 + 30q + 5,

and the firm's marginal cost of production (MC) is:

MC(q)= 3q^2 -20q +30.

The firm's short-run supply curve is given by

O P = q^2 - 10q + 30 + 5/q.

O P = 3q^2 - 20q + 30 for prices above $2.5.

O P =q^2 - 10q +30 for prices above $5.

O P = 3q^2 - 20q + 30 for prices above $5.

O P = q^2 - 10q + 30 for prices above $10.