Three Grades of milk are 1%, 2% and 3% fat by volume. If x gallons of 1 % grade, Y gallons of 2% and Z gallons of 3% grade are mixed to X+Y+Z galllons of 1.5 % grade. What is X in terms of Y and Z

a) y+3z

b)(Y+Z)/4

c)2Y+3Z

d)3Y+Z

e)3Y+4.5 Z

Solutions???