No problem, let's work through this together. We're starting with 5040 and 6403 and adding them all up.

Step 1: We'll start by adding the digits 0 & 3 in column 1 and get 3.

Step 2: We'll start by adding the digits 4 & 0 in column 2 and get 4.

Step 3: We'll start by adding the digits 0 & 4 in column 3 and get 4.

Step 4: We'll start by adding the digits 5 & 6 in column 4 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

So, 5040 + 6403 = 11443.

