Nesting for loops challenge issue

really need help. i dont even know where to start solving this challenge

  **Your code so far**

function multiplyAll(arr) {
let product = 1;
// Only change code below this line

// Only change code above this line
return product;

multiplyAll([[1, 2], [3, 4], [5, 6, 7]]);
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Challenge: Nesting For Loops

Link to the challenge:

you need to make two loops, one inside the other(nested), in order to easily loop throught all elements in the array and its subarrays. A solid example is shown in the challenge description. The desired result, suggests to multiply all the numbers(their product). There is already a variable named product, which you can use to store that value and just gradually multiply it with every number.
[[1, 2], [3, 4], [5, 6, 7]]
(1 x 2) x (3 x 4) x (5 x 6 x 7)
2 x 12 x 210