We search for red balls (neither yellow or black). There are 6 red balls among all 18 balls. Selecting one ball, there is a chance 6/18 that we pull out a red one. 6/18 is the same as 1/3.
So we convert money into numbers 5 pounds of flour is 480 OK. Then we multiply 5*16 we get 80 then 480/80=006. Then we convert money back to numbers and we get 0.006. Answer A is correct.
