Answer:
In view of the units of corn and precious stones delivered by the US, the open-door cost of creating corn is B. 10⁄60.
What is the open-door cost of delivering corn?
The open-door cost of delivering corn to the US would be the number of precious stones that are surrendered to make one unit of corn.
This can be found as:
= Units of jewels/Units of corn
= 10/60 jewels
All in all, choice B is right.