At a loading dock, each worker on the night crew loaded 3/4 as many boxes as each worker on the day crew. If the night crew has 5/6 as many workers as the day crew, what fraction of all the boxes loaded by the two crews did the day crew load? Select the correct option:
A) 4 / 7	B) 5 / 9	C) 6 / 11	D) 7 / 12	E) 8 / 13

Rationale: "let x be the number of workers on the day crew . let y be the number of boxes loaded by each member of the day crew . then the number of boxes loaded by the day crew is xy . the number of boxes loaded by the night crew is ( 5 x / 6 ) ( 3 y / 4 ) = 5 xy / 8 the total number of boxes is xy + 5 xy / 8 = 13 xy / 8 the fraction loaded by the day crew is xy / ( 13 xy / 8 ) = 8 / 13 the answer is e ."
Answer: E