Question 33572
YOUR QUESTION IS AMBIGUOUS.
IF ABC ARE COLLINEAR..THEY ARE ALL ON SAME LINE.SO THEY ARE ALL ONE RAY.
IF WE DISTINGUISH IN DIRECTION THEN AC AND CA ARE DIFFERENT.
IF WE DISTINGUISH BETWEEN START AND END POINTS ALSO THEN WE SHALL HAVE
AB......BA
AC......CA
BC......CB
THAT IS 6 IN ALL NOT 4 AS YOU HAVE MENTIONED...
SO WHAT EXACTLY YOU WANT?
ON THAT BASIS THE ANSWER WILL DEPEND.