One of the most efficient engines ever developed operated between 2100K and 700K. Its actual efficiency is 40%. What percentage of its maximum possible efficiency is this?

Explanation

To solve the problem step by step, we need to determine the maximum possible efficiency of the engine and then find out what percentage of that maximum efficiency is represented by the actual efficiency.

### Step 1: Identify the temperatures
The temperatures given are:
- \( T_1 = 2100 \, K \) (hot reservoir)
- \( T_2 = 700 \, K \) (cold reservoir)

### Step 2: Calculate the maximum possible efficiency
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