Consider the set S of students currently enrolled at courses at Western University, the set P of professors at Western University, and the set C of course offerings in the current semester. Under what circumstances would each of the following relations actually a function? 1. {(s,p)SPs is enrolled in a course taught by p} {(p,s)PSp teaches s} {(p,c)PCp teaches c} 4. {(c,p)CPc is taught by p}