Why I can't register to the MYECOlab?

假设有一个工厂租用地皮共200元，雇佣五个工人200元，设备200元五个工人加一台设备最多能生产100件产品，产品原料费包括所需能源一共一件40元， 生产两件产品需要680元，第三件只需要原料费用40， 边际成本就是40元 生产第四件也只需40元，边际成本没有减少，反而生产的平均成本一直在减少，这是为什么

please explain this in English, thanks.

Can themarginal cost be zero or negative? Why?

If, a factory pay for room 200yuan, employ 5workers salary is 200yuan, buy a machine 200yuan, produce a product needs metarial and electricity about 40yuan. so the factory produces 2 products about680yuan, the third product needs 40yuan, the merginal cost is 40yuan, the forth product needs 40yuan to produce, so the MC don't change, but average cost change from 640 to 340 to 240, what is wrong with my mind.

hello! I'm confused about question b here. The answer is all of the above, but I think actual cost and opportunity cost is different. In my opinion, if I see a movie, the ticket price is actual cost and the oppotunity cost is the time I spend. How can one thing be both oppotunity cost and actual cost? May somothing wrong about my conprehension of the difinition of the twp words

Before I answer your question here, I'd like you to tell me what fixed costs are and what variable costs are. This topic here will be taught in out Microeconomics next term.

Mr.Lin I didn't see this equation clearly on the class. Could you please explain this for me again？[ASTONISHED FACE] THANKS A LOT！

Opportunity Costs:
In microeconomic theory, the opportunity cost of a choice is the value of the best alternative forgone, where a choice needs to be made between several mutually exclusive alternatives given limited resources. Assuming the best choice is made, it is the "cost" incurred by not enjoying the benefit that would be had by taking the second best choice available.
Key Words, Value, Mutually exclusive.

Example of Opportunity Cost
Q: Suppose you have a free ticket to a concert by Band A. The ticket has no resale value. On the night of the concert your next-best alternative entertainment is a performance by Band B for which the tickets cost $40. You like Band B and would usually be willing to pay $50 for a ticket to see them. What is the opportunity cost of using your free ticket and seeing Band A?
A: The benefit you forgo (that is, the value to you) is the benefit of seeing Band B. As well as the gross benefit of $50 for seeing Band B, you also forgo the actual $40 of cost, so the net benefit you forgo is $10. So, the opportunity cost of seeing Band A is $10.

Capital
For economists, capital includes all manufactured aids used in producing consumer goods and services. Included are all factory, storage, transportation, and distribution facilities, as well as tools and machinery.
Capital used by economists refers no to money but to tools, machinery, and other productive equipment. Because money produces nothing, economists do not include it as an economic resource. Money is simply a means for purchasing goods and services, including capital goods.

Hello, @DlinKean I want to wonder the differences between trade-off and opportunity cost.

is marginal cost also a kind of explicit cost?

is the economic profits smaller than the accounting profits?