During the course of the spring semester at the School of Nursing (SON), 13 students developed colds

During the course of the spring semester at the School of Nursing (SON), 13 students developed colds. There are 22 students who enrolled in the SON for the first time at the start of the spring semester (new to school), and 88 students are continuing at the school from the previous fall semester. Thirty-two students had a cold at some point during the spring semester. According to a survey done by students at the SON on the last day of the spring semester, three students claimed to have a cold at the time of the survey.

• What was the point prevalence per 1,000 of colds at the time of the survey?

• What was the incidence per 1,000 of colds during the spring semester?

• What was the period prevalence per 1,000 of colds during the spring semester?