Let's roll up our sleeves and solve this. We have 128 and we're going to multiply it by 4, essentially adding 128 to itself 4 times.
Step 1: 0 + 128 = 128
Step 2: 128 + 128 = 256
Step 3: 256 + 128 = 384
Step 4: 384 + 128 = 512

So, 128*4 = 512