If the diameter of circle R is 80% of the diameter of circle S, the area of circle R is what percent of the area of circle S?	Select:
A) 74 %
B) 64 %
C) 84 %
D) 94 %
E) 34 %

Rationale: "let diameter of circle r , dr = 80 and diameter of circle s , ds = 100 radius of circle r , rr = 40 radius of circle s , rs = 50 area of circle r / area of circle s = ( pi * rr ^ 2 ) / ( pi * rs ^ 2 ) = ( 40 / 50 ) ^ 2 = ( 8 / 10 ) ^ 2 = 64 % answer : b"
Answer: B