The work of a student to find the dimensions of a rectangle of area 8 + 16x and width 4 is shown below:

Step 1: 8 + 16x
Step 2: 4(4) + 4(12x)
Step 3: 4(4 + 12x)
Step 4: Dimensions of the rectangle are 4 and 4 + 12x

In which step did the student first make an error and what is the correct step?