John makes $50 a week from his job. He earns a raise andnow makes $90 a week. What is the % increase?
Choose the correct choice from the following answers.
A) 15 %  B) 16.66 %  C) 17.8 %  D) 80 %  E) 21 %

Rationale: "increase = ( 40 / 50 ) * 100 = ( 4 / 5 ) * 100 = 80 % . d"
Answer: D