In a warehouse, a dozen eggs and 10 apples had the same price. After a week, the price of eggs dropped by $10 \%$ and the price of apples increased by $2 \%$. How much more will be spent on the purchase of a dozen eggs and 10 apples?
(a) $2 \%$
(b) $4 \%$
(c) $10 \%$
(d) $12 \%$
(e) $12.2 \%$

## Solutions to List 3
Suppose, initially, that a dozen eggs cost $R \$ 1.00$. Thus, 10 apples also cost $R \$ 1.00$. Since the price of eggs increased by $10 \%$, the new price of eggs is $R \$ 1.10$. The price of apples decreased by $2 \%$, so the new price of apples is $R \$ 0.98$.

Thus, before it cost 2 reais to buy 1 dozen eggs and 10 apples, now it costs $1.10+0.98=2.08$. Therefore, the increase was $R \$ 0.08$, which corresponds to the percentage:

$$
\frac{0.08}{2}=0.04=\frac{4}{100}=4 \%
$$

The correct option is (b).