Explain how, using a Polaroid and a quarter-wave plate made of positive uniaxial crystal (ne > no),

Question:

Explain how, using a Polaroid and a quarter-wave plate made of positive uniaxial crystal (ne > no), to distinguish
(a) Light with left-hand circular polarization from that with right-hand polarization;
(b) Natural light from light with circular polarization and from the composition of natural light and that with circular polarization.