First find the total for Belinda and Cindy, then express Amy as a fraction of that sum.<br><br>
&bull; Ratio = \(4 : 1 : 5\)<br>
&bull; Belinda + Cindy = \(1 + 5 = 6\) parts<br>
&bull; Amy = 4 parts<br>
&bull; \(\frac{\text{Amy}}{\text{Belinda} + \text{Cindy}} = \frac{4}{6} = \frac{2}{3}\)<br><br>
Final Answer: A = 2, B = 3