Dear prof. Lin,
Consumers increase the quantity of products, which shows in curve D1 to D2, indicates that there is an increase in income of consumers, isn't it? Why the correct answer is "All the above"? It is obvious that A is the opposite of C.

Dear professor Lin, can you explain why when the expected future price increases,quantity supply will decrease.What i argue now is that the expected future price increases illustrates more people want to buy product or service. In other words, this product or service is popular.So why do rational producer not produce more quantity to gain more profit?

why don't choose B?

Hi Lin. Why we choose this choice? I think the increase in demand will lead to Market Equilibrium. Although there are 100 customers shifting to X, there will be less when it reaches the Market Equilibrium.

Hello David After chapter 3,which chapter will we learn next?

Hi David,
Can good A's supply decrease lead it's complementary good B's demand decrease directly?

Professor:
I suggest you can set some exercises for us because I find the test is more harder than our homework, we need more practise to deal with the test, and as the score come out we cannot review which exercise we did wrong, so if next time we face the same situation we will also make mistakes, can you let us see which we did wrong so we can correct next time.

I don't know the meaning of the sign,thanks.

Why not the opportunity cost equals to 4 machine-made cigars minus 10 dollars?

Professor, could you show me the calculation of these two questions? I'm poor at calculating and I can't figure out the answer.