1.2: Sector area and shaded region in a rectangle

The diagram shows a circle, centre $O$, radius $12\text{ cm}$. The points $A$ and $B$ lie on the circumference of the circle and form a rectangle with the points $C$ and $D$. The length of $AD$ is $8\text{ cm}$ and the area of the minor sector $AOB$ is $150\text{ cm}^2$.