The Frequency of Sickle Cell Anemia,caused by a Homozygous Condition

The frequency of sickle cell anemia,caused by a homozygous condition (Hb^sHb^s) is approximately 0.0016.The normal condition is also a homozygous condition (Hb^AHb^B) .Assuming the Hardy-Weinberg equilibrium applies,what is the frequency of the Hb^s allele?

A) 0.0004
B) 0.04
C) 0.4
D) 0.9216
E) 0.96