How many 4-letter code can be formed using the first 10 letters of the English alphabet, if no letter can be repeated?

Explanation

To solve the problem of how many 4-letter codes can be formed using the first 10 letters of the English alphabet without repeating any letters, we can follow these steps:

### Step 1: Identify the total number of letters available
We have the first 10 letters of the English alphabet, which are: A, B, C, D, E, F, G, H, I, J.

### Step 2: Determine the number of choices for each position in the code
Since we are forming a 4-letter code and no letter can be repeated, we will calculate the number of choices for each of the 4 positions in the code:

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