A rectangle has vertices at (Negative1, 6), (Negative1, Negative2), (3, 6), and (3, Negative 2). Sara says the area of the rectangle is 16 square units and her work is shown below.

Steps
Sara’s Work
Step 1
Base: StartAbsoluteValue negative 1 EndAbsoluteValue + StartAbsoluteValue 3 EndAbsoluteValue = 4
Step 2
Height: StartAbsoluteValue 6 EndAbsoluteValue + StartAbsoluteValue negative 2 EndAbsoluteValue = 4
Step 3
Area: 4 times 4 = 16 square units

Where, if at all, did Sara first make a mistake in finding the area of the rectangle?
Step 1
Step 2
Step 3
no mistake