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