**Tell us what’s happening:**

Hi, I am really stuck with this one. Though I understand recursion through other examples, I can’t figure out how this example works.

What is happening in the line below between the two parameters arr and n-1? What is being multiplied ? What makes me confused is that the function has two paramenters: arr and n. I don’t understand their relationship here.

```
return multiply(arr, n - 1) * arr[n - 1];
```

Thanks for any help, really appreciated!

**Your code so far**

```
function sum(arr, n) {
// Only change code below this line
// Only change code above this line
}
```

**Your browser information:**

User Agent is: `Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.149 Safari/537.36`

.

**Challenge:** Replace Loops using Recursion

**Link to the challenge:**