Alright, let's solve this problem step by step. We have 2001 and 4001 and we're adding them together.

Step 1: We'll start by adding the digits 1 & 1 in column 1 and get 2.

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

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

Step 4: We'll start by adding the digits 2 & 4 in column 4 and get 6.

So, 2001 + 4001 = 6002.

