Leela stops to get some food at Fishy
Joe's and she sees that 40% of the salads have cheese topping on them, 20% have
ranch on them, and 40% are plain. Of the salads with cheese topping, 45% have
"froot" on them; of the salads with ranch, 15% have "froot"
on them; and of the plain salads, only 10% have froot on them. Leela tells the
clerk to choose a salad for her at random. Given that the salad does not have "froot",
what is the probability that it is a plain salad?