93. While waiting in line to buy two tacos at 80 cents each and a medium drink for 90 cents, Kayla notices
that the restaurant has a value meal containing three tacos and a medium drink all for $3. For Kayla,
the marginal cost of the third taco would be
94. While waiting in line to buy one cheeseburger for $1.50 and a medium drink for $1.00, Sally notices
that she could get a value meal that contains both the cheeseburger and medium drink and also a
medium order of fries for $2.75. She thinks to herself, “Is it worth the extra 25 cents to get the medium
fries?” To an economist, Sally’s decision is an example of
marginal decision making.
basing decisions on total, rather than marginal, value.
an unintended consequence.
the fallacy of composition.
95. Isabella wishes to buy gasoline and have her car washed. She finds that if she buys 9 gallons of
gasoline at $1.50 per gallon, the car wash costs $1, but if she buys 10 gallons of gasoline, the car wash
is free. For Isabella, the marginal cost of the tenth gallon of gasoline is
96. Santiago wants to buy some milk and a box of cereal. If he buys 2 quarts of milk at $1 per quart, the
box of cereal costs 75 cents. If he buys 3 quarts of milk at $1 per quart, the box of cereal is free. For
Santiago, the marginal cost of the third quart of milk is
97. A firm producing cans buys three tons of aluminum per day at $200 per ton. If it buys four tons per
day, it receives a quantity discount on all units and pays only $175 per ton. The marginal cost of the
fourth ton per day is