12. Consider a consumer facing prices $6 for good 1 and $3 for good 2. Which statement is true?

a. The opportunity cost of 1 unit of good 1 is 0.5 units of good 2, on the consumer's budget constraint.

b. The opportunity cost of 1 unit of good 1 is 1 units of good 2, on the consumer's budget constraint.

c. The opportunity cost of 1 unit of good 1 is 6 units of good 2, on the consumer's budget constraint.

d. The opportunity cost of 1 unit of good 1 is 2 units of good 2, on the consumer's budget constraint.

e. The opportunity cost of 1 unit of good 1 is 3 units of good 2, on the consumer's budget constraint.