Given the table below comparing the marginal benefit Lucinda gets from
Kewpie dolls and Beanie Babies.
[tex]\begin{tabular}
{|p {2cm}|p {2cm}|p {2cm}|p {2cm}|}
\multicolumn {4} {|c|} {Lucinda's Kewpie Doll and Beanie Baby Marginal Benefits}\\[1ex]
\multicolumn {2} {|c|} {Kewpie Dolls}&\multicolumn {2} {|c|} {Beanie Babies}\\[1ex]
1&\$15.00&1&\$12.00\\
2&\$12.00&2&\$10.00\\
3&\$9.00&3&\$8.00\\
4&\$6.00&4&\$6.00\\
5&\$3.00&5&\$4.00\\
6&\$0.00&6&\$2.00\\
\end{tabular}[/tex]
If
lucinda has only $18 to spend and the price of kewpie dolls and the
price of beanie babies are both $6,
Lucinda will buy the combination for which marginal benefit is the same.
Therefore, Lucinda will buy 2 kewpie dolls and 1 beanie baby,
if she were rational.