Some of 50%-intensity red paint is replaced with 25% solution of red paint such that the new paint intensity is 45%. What fraction of the original paint was replaced? Choose the correct answer:
A) 1 / 30	B) 1 / 5	C) 2 / 3	D) 3 / 4	E) 4 / 5

Rationale: "45 % is 20 % - points above 25 % and 5 % - points below 50 % . thus the ratio of 25 % - solution to 50 % - solution is 1 : 4 . 1 / 5 of the original paint was replaced . the answer is b ."
Answer: B