The shaded region is a rectangle, the area of the shaded region is 48 mm²
How to determine the area of the shaded region?
From the complete question, the shaded region has the following properties
Shape: Rectangle
Length = 12 mm
Width = 4 mm
The area is then calculated as:
Area = Length * Width
This gives
Area = 12 mm * 4 mm
Evaluate
Area = 48 mm²