In how many ways can 5 letters be posted in 4 letter boxes?

Explanation

To solve the problem of how many ways 5 letters can be posted in 4 letter boxes, we can break it down step by step.

### Step-by-Step Solution:

1. **Identify the Variables**:
- We have 5 letters (let's denote them as A1, A2, A3, A4, A5).
- We have 4 letter boxes (let's denote them as L1, L2, L3, L4).

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