Please refer to the illustration at screenshots<dot>firefox<dot>com/jZoizoMJf8a3H0UZ/ds055uzetaobb<dot>cloudfront<dot>net
to help answer the following question:
Zeb's coin box contains 8 fair, standard coins (heads and tails) and 1 coin which has heads on both sides. He selects a coin randomly and flips it 4 times, getting all heads. If he flips this coin again, what is the probability it will be heads?