## 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
Lipid-nanoparticle (LNP) formulation dataset for cannabidiol (CBD) drug delivery. 768 experiments measure how input ingredients affect drug-loading capacity, encapsulation efficiency, and particle size.

### 2. Variable List
| Variable | Type | Values | Meaning |
|----------|------|--------|---------|
| drug_input | discrete | 4 levels | amount of CBD fed |
| solid_lipid | categorical | 3 types | chemical type of solid lipid |
| solid_lipid_input | discrete | 4 levels | mass ratio of solid lipid |
| liquid_lipid_input | discrete | 4 levels | mass ratio of liquid lipid |
| surfactant_input | discrete | 4 levels | mass ratio of surfactant |

### 3. Task Description
Maximise **encap_efficiency**.