Rachel and her spouse, Ross, held a party last night to celebrate their 1st Wedding Anniversary. They invited 4 other couples to the party. As the party progressed, Rachel discovered that, prior to the party, each person except her knew a different number of the people who were present at the party. Assuming that if Person A knew Person B, Person B also knew Person A, how many people did Ross know prior to the party? Also, how many people did Rachel know? Provide a detailed explanation along with your answer.