Drum X is 1/2 full of oil and drum Y, which has twice the capacity of drum X, is 1/3 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
A) 2 / 3  B) 5 / 6  C) 7 / 12  D) 11 / 12  E) 17 / 24

Rationale: "( 1 / 2 ) x = ( 1 / 4 ) y ( 1 / 4 ) y + ( 1 / 3 ) y = ( 7 / 12 ) y the answer is c ."
Answer: C