There is a total of 100 marbles in a box, each of which is red, green, blue, or white. If one marble is drawn from the box at random, the probability that it will be white is 1/4 and the probability that it will be green is 1/5. What is the probability that the marble will be either red or blue?	Select the correct option.
A) 2 / 3 B) 3 / 5 C) 7 / 10 D) 9 / 20 E) 11 / 20

Rationale: "p ( red or blue ) = 1 - p ( white ) - p ( green ) = 20 / 20 - 5 / 20 - 4 / 20 = 11 / 20 the answer is e ."
Answer: E