The correct answer is - b. highest, lowest.
The supplier of goods (in this case the cookies) always tends to maximize the profit, thus looks for ways to increase the prize as much as possible, while still keeping the good attractive for the consumers.
The consumers, on the other hand, tend to demand goods for prices as lower as possible, while still getting the same quality of the goods.
Naturally, the both perspectives and actions balance themselves, with the end result being a price equilibrium, where the price will be good enough for both sides, though the tendencies for the primary goals will continue.
