There are 6 coins in a box. 2 are two-headed coins, 1 is a two-tailed coin, and the remaining 3 coins are fair coins.

When one of the 6 coins is chosen at random and flipped, it shows a head.

Find the probability that the chosen coin is a fair coin.

a.

0.4286

b.

0.5000

c.

0.2500

d.

0.5833