宏观经济问题,成本曲线Supposethe marginal cost of two plants of a firm

初级宏观经济题目
Artland can produce 600 hats or 300 bicycles whereas Rayland can produce 1200 hats or 300 bicycles
Q:
1)calculate the opportunity cost of a bicycle in Artland
2)if the 2 countries specialize and trade, which country will import bicycles? explain!
3)if the terms of trade are 5 hats for 1 bicycle, would trade be advantageous for each of the following? (1) Artland (2)Rayland
刚刚接触宏观经济,所以想请教一下答题思路是否正确
第一题：A 生产1 bicycle就可以生产2 hats,根据定义,所以the opportunity of a bicycle 就是舍弃掉的2 hats 对吗?
至于第二题,不是很能解释得清楚……是R吗?
第三题,我觉得是……不行,完全混乱了……
赐教赐教~~~~
both of the countries use equal amounts of resouces