a. PS→+SF→+YG→−+FY→−+WP→−+GW→− == PS→+SF→+FY→+YG→+WP→+GW→ == PS→+SF→+FY→+YG→+WP→−GW→ == PS→+SF→+FY→+YG→WP→-GW→ == PS→+SF→+FY→+WP→+YG→-GW→ == PS→+SF→+FY→+WP→+YG→ == PS→+SF→+FP→+WG→ == PS→+SG→+FP→+WG→ == PS→+SG→+GP→+WG→ == PS→+SG→+GP→+FW→ == PS→+SG→+GP→+FW→ == PS→+SG→+GP→FW→ == PS→+SG→+PF→= 0
b. SG→+GP→+FW→+PF→ == SG→+GP→+FW→+PF→ == SG→+GP→+FW→PF→ == SG→+GP→WF→ == SG→+PF→= 0
a. PS→+SF→+YG→−+FY→−+WP→−+GW→− =
= PS→+SF→+FY→+YG→+WP→+GW→ =
= PS→+SF→+FY→+YG→+WP→−GW→ =
= PS→+SF→+FY→+YG→WP→-GW→ =
= PS→+SF→+FY→+WP→+YG→-GW→ =
= PS→+SF→+FY→+WP→+YG→ =
= PS→+SF→+FP→+WG→ =
= PS→+SG→+FP→+WG→ =
= PS→+SG→+GP→+WG→ =
= PS→+SG→+GP→+FW→ =
= PS→+SG→+GP→+FW→ =
= PS→+SG→+GP→FW→ =
= PS→+SG→+PF→
= 0
b. SG→+GP→+FW→+PF→ =
= SG→+GP→+FW→+PF→ =
= SG→+GP→+FW→PF→ =
= SG→+GP→WF→ =
= SG→+PF→
= 0