Consider the vectors a = 1+23 - k, b=27+3-k, c=-1-23+ k d = - itj+ k, g=-1- 3+2k. Which pairs (if any) of these vectors are (a) Are perpendicular? (Enter none or a pair or list of pairs, e.g., if a is perpendicular to b and c, enter (a,b), (a,c).) (b) Are parallel? (Enter none or a pair or list of pairs, e.g., if a is parallel to b and , enter (a,b), (a,c).) (c) Have an angles less than 7 /2 between them? (Enter none or a pair or list of pairs, e.g., if a is at an angle less than pi/2 from b and c, enter (a, b),(a,c).) (d) Have an angle of more than 7/2 between them? (Enter none or a pair or list of pairs, e.g., if a is at an angle greater than pi/2 from b and c, enter (a,b), (a,c).)