There are four boxes that look the same. In one box (the special box), half of the marbles are blue. But only 1/8 of the marbles in the other boxes are blue. You pick a box at random and randomly select a marble from it. The marble is blue. What should your new odds be that the box you picked is the special one?

a 4 : 3

b 4 : 7

c 3 : 4

d 8 : 7