Find the fraction of the total potion that is snake blood, then multiply by the total volume.<br><br>
&bull; Snake blood : Bat saliva = \(10 : 25 = 2 : 5\)<br>
&bull; Total parts = \(2 + 5 = 7\)<br>
&bull; Snake blood fraction = \(\frac{2}{7}\)<br>
&bull; \(\frac{2}{7} \times 420 = 120\) ml<br><br>
Final Answer: 120