The area of the washer will be found by calculating the area of the shaded part.
Area of larger circle:
A=πr²
r=4.4+(13.2/2)=11 mm
thus
A=π×11²=380.13
Area of the small circle:
A=π×(13.2/2)²=136.85 mm
The area of the washer will be:
380.13-136.85
=243.28
~243.3 mm²
