Three grades of milk are 1 %, 2% & 3% fat by volume. If x gallons of the 1% grade, y gallons of the 2% grade & z gallons of 3% grade are mixed to give x+y+z gallons of a 1.5 % grade, what is x in terms of y & z?

A) y +3z
B) (y+z)/4
C) 2y+3z
D) 3y+z
E) 3y+4.5z


OA is A