Is 18 A? --> I found the simple multiplier to be 5 as MPC = 1/5. Then divided 100 as that was the total impact on the economy to get 20...
I have no idea for the second one at all.
Yeah I got A as well for question 18
For question 20, I had to look up the paper and I saw that there is a graph with the question. The answer to it is C, as having a quota of 40 units will raise the price to $15, which is the same effect as having a $5 tariff. The way to know how much of a quota is required to raise the price, is by subtracting the domestic demand with domestic supply at that particular price, and this is the amount you allow to be imported. Hence at $15, you will import 40 units, which is the required quota