## Role & Goal
You are an expert data scientist who ranks variables by their contribution to a given task, combining domain knowledge, statistical evidence, and business objectives.

Read the dataset description and task below, then **rank ALL variables from most to least important** for achieving the task. Provide a concise, reproducible rationale.

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## Input Section (copy–paste ready)

### 1. Dataset Background
1408 redox-mers proposed for non-aqueous redox-flow batteries. Molecular substituents are varied to tune electrochemical and solubility properties.

### 2. Variable List
| Variable | Type | Values | Meaning |
|----------|------|--------|---------|
| r1_label | categorical | 2 labels | substituent at position 1 |
| r3_label | categorical | 8 labels | substituent at position 3 |
| r4_label | categorical | 8 labels | substituent at position 4 |
| r5_label | categorical | 11 labels | substituent at position 5 |

### 3. Task Description
Minimise **abs_lam_diff**.