How many ounces of a 60% salt solution must be added to 50 ounces of a 20 percent salt solution so that the resulting mixture is 40% salt?  Choose the most appropriate option:  A) 16.67  B) 30  C) 50  D) 60.33  E) 70

Rationale: "for 60 % salt solution ( x ) and 20 % salt solution ( y ) to give 40 % = ( 60 + 20 ) / 2 salt solution , we should mix equal amounts of x and y . answer : c ."
Answer: C