Can someone please enter a number answer for a, b, and c. Thank you :)

An experiment consists of recording the sex composition, in order of their births, of a four- child family in which the children were born at different times. Assuming that a boy is equally likely as a girl to be born into a family, what is the probability that a four-child family chosen at random will have the following? (a) Three boys and a girl in the family (b) A youngest child in the family who is a girl (c) An oldest child and a youngest child in the family who are both girls