[SYSTEM]
You are answering a single information-extraction question. Use ONLY the supplied source material. Do not use prior knowledge. Give a clear, concrete answer with the specific number, name, year, or value asked for.

[USER]
--- SOURCE ARTIFACT (M3-L4) ---
# Table 135 — No caption detected.

PDF page: 584

```csv
Ratio of concentrations of heavy metals used in the mixture (Chiral sta n the mixture (Chiral sta.,r rt r Artemia,Synergism.\ ia \ Acartia
120,II,II
LEBaL,20,be)
T2205 0k,35,8
25:1,32,5
5OuE,22,12
100:1,18,16
400:1,26,14
```

--- END ARTIFACT ---

Question:
A toxicology table in Vol 35 records the survival rate of Artemia exposed to mixtures of two heavy metals at different concentration ratios. The table includes entries at ratios of 100:1 and 400:1, but no entry at 250:1. Estimate the survival rate at a 250:1 concentration ratio by linear interpolation between the two bracketing ratio entries.

Answer concisely. Cite the row/cell/section you used. State your final numerical answer clearly.