Use the unit method. Let the total money be 9 units.<br><br>
&bull; Mother: \( \frac{4}{9} \) of total = 4 units<br>
&bull; Remaining: 9 − 4 = 5 units<br>
&bull; Father: \( \frac{2}{5} \) of remaining = \( \frac{2}{5} \times 5 \) = 2 units<br>
&bull; Money left: 5 − 2 = 3 units<br>
&bull; Fraction left: \( \frac{3}{9} = \frac{1}{3} \)<br><br>
Final Answer: A: \( \frac{1}{3} \)