(2) The profit of a perfectly competitive enterprise is always maximized, with marginal cost = average income = 10.

(3) With the entry of more manufacturers in the perfectly competitive market, the excess profit of enterprises gradually decreases until the long-term profit is zero.

2. Private savings = y-t-c =10000-1500-6000 = 2500, public savings = t-g =1500-1700 =-200 national savings =

3. As a mathematical function, find the maximum value of the element. When n=0, it is the extreme value of function elements, and this extreme value is also the maximum value of T. The derivative of function x=R(Q)-C(Q) =MR(Q)-MC(Q)=0, that is, in the short-term completely competitive market, the manufacturer's MR=P is a fixed-value cost function that decreases first and then increases, so 7 is a fixed-value cost function that increases first.

4. Economic profit can be understood as excess profit, which means that the price is higher than the average cost, and the production efficiency of enterprises adopting new technologies is higher than that of other enterprises in the industry. As for the problem of profit maximization, it can be regarded as the extra income brought by the reduction of its own cost. Sir & gtMC means that it is still profitable to produce one more unit of products, and the enterprise will continue to produce MR5. No matter what market structure, perfect competition, monopoly competition or oligopoly, the condition of maximizing the profit of a manufacturer is that the marginal cost is equal to the marginal income, that is, MC = Mr Under the condition of perfect competition, the products are homogeneous, all the goods produced by the manufacturer are exactly the same, the price is P, and the marginal income of the manufacturer is the price P of the unit product. Therefore, under the condition of perfect competition, when the profit is maximized, MC=MR=P is satisfied.

What are the advantages and disadvantages of the profit maximization goal?

1. Advantages: The calculation of profit index is simple and easy to understand. Conducive to the rational allocation of enterprise resources and the improvement of the overall economic benefits of enterprises;

2. Disadvantages: Failure to consider the time when profits are realized and the time value of funds, failure to consider risks, and failure to reflect the relationship between the profits created and the invested capital may lead to the short-term tendency of financial decision-making of enterprises and affect the long-term development of enterprises.