At a loading dock, each worker on the night crew loaded 1/2 as many boxes as each worker on the day crew. If the night crew has 4/5 as many workers as the day crew, what fraction of all the boxes loaded by the two crews did the day crew load?  Choose one: A) 1 / 2 B) 2 / 5 C) 3 / 5 D) 4 / 5 E) 5 / 7

Rationale: "method : x = no . of boxes loaded by day crew . boxes by night crew = 1 / 2 * 4 / 5 x = 2 / 5 x % loaded by day crew = x / ( x + 2 / 5 x ) = 5 / 7 answer e"
Answer: E