In the given figure O and O2 are the centre of the bigger circle of radius 3 cm and the smaller circle of radius 1.5 cm respectively and O1 is the centre of the semi-circle of radius 1 cm, all lying on diameter AB. Find the area of shaded region.
A92/7 cm2
B88/7 cm2
C89/21 cm2
D18/7 cm2