In some future time, once bars may open again, Alice and her partner Bob head over to indulge in this way of socializing again. There are four other couples in the bar which, eager for social contact, do these cute footshakes with each person they haven't met before. After this initial mingling, Alice asks everyone how many people they did footshakes with. As some people knew each other beforehand, she gets nine different answers back.
How many footshakes did Bob do?