a) $(1+ \sqrt 3)P$ in direction $120 ^{\circ}$ with that of A
b) $(1+ \sqrt 3)P$ in direction $150 ^{\circ}$ with that of A
c) $2P$ in direction $150 ^{\circ}$ with that of A
d) $2P$ in direction $150 ^{\circ}$ with that of B