Okay, we are given 4386 and 4004. Let's add them up step by step.

Step 1: We'll start by adding the digits 6 & 4 in column 1 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 8 & 0 in column 2 and get 9.

Step 3: We'll start by adding the digits 3 & 0 in column 3 and get 3.

Step 4: We'll start by adding the digits 4 & 4 in column 4 and get 8.

So, 4386 + 4004 = 8390.

