PLEASE THIS IS DUE IN 10 MINS AND IM STUCK ON MY LAST QUESTION!!! Which relation is not a function?
a
{(4,7),(2,1),(-3,6),(3,4)}
b
{(-1,6),(1,3),(2,5),(1,7)}
c
{(1,5),(2,6),(3,6),(4,7)}
d
{(-1,2),(0,5),(5,0),(2,-1)}