Answer: d). 50 units of grain and 130 units of incense.
Explanation: Comparative advantage for a country exists when it has a lower opportunity cost of producing a good as compared to the other country.
As given in the problem, a worker in agland can produce either 10 units of organic grain or 2 units of incense per year, and a worker in zenland can produce either 5 units of organic grain or 15 units of incense per year.
This, means that opportunity cost of producing organic grain in Agland is 0.2 i.e (2/10) and that in Zenland is 3 i.e (15/5). Thus, clearly Agland has a lower opportunity cost in production of organic grain. Thus, it will specialise in organic grain production , producing a total of 200 units of organic grain i.e (10*20 workers).
Similarly, Zenland has a lower opportunity cost in incense production which is 0.33 i.e(5/15) in comparison to 5 i.e(10/2) of Agland. So, Zenland will produce only Incense making a total of 150 units of incense (15* 10 workers).
Thus, before trade total organic grain produces was

Before trade incese produced was,

While, after trade the two countries produce a total of 200 units of organic grain and 150 units of incense.
Thus, increase in organic grain production is
and of incense is 
Thus, the correct answer is 50 units of grain and 130 units of incense.