Genes on the X chromosome in humans

Hemophilia is determined by genes on the X chromosome in humans. Assume that a phenotypically normal woman whose father had hemophilia is married to a normal man. 1) What is the probability that their first son will have hemophilia? 2) What is the probability that their first daughter will have hemophilia? A. 100%; B. 50%; C. 25% D. 0% Please explain your answering and reasoning.