Each of the products produced yesterday was checked by worker x or worker y. 0.5% of the products checked by worker x are defective and 0.8% of the products checked by worker y are defective. If the total defective rate of all the products checked by worker x and worker y is 0.65%, what fraction of the products was checked by worker y?  Choices.
A) 1 / 5 B) 1 / 2 C) 2 / 3 D) 1 / 4 E) 2 / 5

Rationale: "x : 0.5 % is 0.15 % - points from 0.65 % . y : 0.8 % is 0.15 % - points from 0.65 % . therefore the ratio of products checked by y : x is 1 : 1 . thus , worker y checked 1 / 2 of the products . the answer is b ."
Answer: B