Some of 40%-intensity red paint is replaced with 20% solution of red paint such that the new paint intensity is 20%. What fraction of the original paint was replaced?	Select the correct option:
A) 2 / 5
B) 2 / 3
C) 1 / 3
D) 1 / 2
E) 1 / 1

Rationale: "let total paint = 1 let amount replaced = x 40 ( 1 - x ) + 20 x = 20 x = 1 / 1 answer : e"
Answer: E