A deposit of shale oil is discovered in an area of farming.
The following estimates are made for a ten-year period.
• If the land is used only for farming it would yield income after tax of $10 billion.
• If the land is used only for shale oil extraction it would yield income after tax of
$40 billion.
• The government would receive $5 billion in taxes from farming and $10 billion in
taxes from shale oil extraction.
What is the opportunity cost of using the land only for farming?
A. $25 billion
B. $30 billion
C. $35 billion
D. $45 billion