Suppose a country's workers can produce 4 pens per hour or 12 pencils per hour. If there is no trade, ________. a. the opportunity cost of 1 pen is 4 pencils b. the opportunity cost of 1 pen is 1/4 of a pencil c. the opportunity cost of 1 pen is 3 pencils d. the opportunity cost of 1 pen is 12 pencils e. the opportunity cost of 1 pen is 1/3 of a pencil