Ester goes to a stationery store to buy notebooks and pens. In this stationery store, all notebooks cost $\mathrm{R} \$ 6.00$. If she buys three notebooks, she will have R \$4.00 left. If, instead, her brother lends her an additional $\mathrm{R} \$ 4.00$, she will be able to buy two notebooks and seven pens, all the same.

(a) How much does each pen cost?

(b) If she buys two notebooks and does not borrow money, how many pens can Ester buy?
By buying three notebooks at 6 reais each, Ester still has 4 reais left, so the amount she has is $3 \times 6 + 4 = 22$ reais.

(a) If her brother lends her 4 reais, she then has $22 + 4 = 26$ reais and can buy 2 notebooks at 6 reais each, leaving her with $26 - 2 \times 6 = 26 - 12 = 14$ reais for 7 pens. We conclude that the price of each pen is $14 \div 7 = 2$ reais.

(b) Since Ester has 22 reais, if she buys 2 notebooks, she will have $22 - 2 \times 6 = 22 - 12 = 10$ reais left. Since each pen costs 2 reais, she can buy $10 \div 2 = 5$ pens.