Three vectors a, b, and c  each have a magnitude of
50 m and lie in an xy plane. Their directions relative to the positive
direction of the x axis are 30°, 195°, and 315°, respectively. What are
(a) the magnitude and (b) the angle of the vector 7i  +  b +  c, and
(c)  the magnitude  and (d) the angle of a - b +  c? What are the
(e)  magnitude  and  (f)  angle  of  a  fourth  vector  d such  that
(a + b) - (c + d)  =  O?