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?

The marginal cost of the third taco would be - $0.5.

Explanation:

Kayla wants to buy two tacos at 80 cents each and a medium drink for 90 cents.

Her total spending on two tacos and a drink is

=.80 * 2 +.90

= 1.6 +.90

= $2.5

A value meal containing three tacos and a medium drink is worth $3.

The marginal cost of the third Taco will be

= $2.50 - 43

= - $0.5 or 50 cents