Drum X is 1/2 full of oil and drum Y, which has twice the capacity of drum X, is 1/5 full of oil. If all of the oil in drum X is poured into drum Y, then drum Y will be filled to what capacity?  Select the correct option
A) 3 / 10	B) 7 / 10	C) 9 / 10	D) 9 / 20	E) 13 / 20

Rationale: "( 1 / 2 ) x = ( 1 / 4 ) y ( 1 / 4 ) y + ( 1 / 5 ) y = ( 9 / 20 ) y the answer is d ."
Answer: D