IKMC 2007 - Grades 11-12 - Self-study Question 15

Question 15

Two semicircles are drawn as shown. Chord $CD$ of the larger semicircle has length 4, is parallel to its diameter $AB$, and is tangent to the smaller semicircle. What is the shaded area?

Question illustration

$\pi$
$1.5\pi$
$2\pi$
$3\pi$
Not enough information