We will assume that the birth of a girl and a boy is equally probable. It is known that in some family there are two children.
a) What is the probability that one of them is a boy and one a girl?
b) Additionally, it is known that one of the children is a boy. What is the probability that there is one boy and one girl in the family now?
c) Additionally, it is known that the boy was born on a Monday. What is the probability that there is one boy and one girl in the family now?