If a2 - b2 = 8 and a*b = 2, find a4 + b4.	Choose the correct choice from the following:
A) 62
B) 72
C) 82
D) 92
E) 62

Rationale: "a 2 - b 2 = 8 : given a 4 + b 4 - 2 a 2 b 2 = 82 : square both sides and expand . a * b = 2 : given a 2 b 2 = 22 : square both sides . a 4 + b 4 - 2 ( 4 ) = 82 : substitute a 4 + b 4 = 72 correct answer b"
Answer: B