Inference I suggests that there is no tree whose production is less than 1200. However, the given statement only tells us that the average production is 1200. It does not guarantee that each tree produces exactly 1200 or that there are no trees producing less. Hence, Inference I does not follow.
Inference II suggests that mango farming is more beneficial than other kinds of farming, but the statement does not provide any information or comparison with other types of farming. Thus, Inference II also does not follow.
The correct answer is (a) Neither inference I nor inference II follows.