Hamburgers cost \($2\) and hot dogs cost \($1\), and Juan is in consumer equilibrium. What must be true about the marginal utility of the last hamburger Juan consumes?

a. The marginal utility of the last hamburger consumed must be less than that of the last hot dog.

b. The marginal utility of the last hamburger consumed must be equal to that of the last hot dog.

c. The marginal utility of the last hamburger consumed must be greater than that of the last hot dog.

d. The marginal utility of the last hamburger consumed must be equal to zero.