1, A/B efficiency:1/3÷ 5 =115.
2. Efficiency of ethylene-propylene copolymer: (1-1/3) ×1/4 ÷ 2 =112.
3. Efficiency of A, B and C:1-1/3-(1-1/3) ×1/4 =1/8.
4. Efficiency:1/8-115 = 7/120.
5.a Efficiency:1/8-112 =1/24.
6. Efficiency:115-1/24 =1/40.
7. The money earned by Party A (Party A works for 9 days): 2280× 1/24× (4+5) = 855 (yuan).
8. Money received by Party B (Party B's work 1 1 day): 2280 × 1/40 × (5+2+4) = 627 (yuan).
9. The money received by Party C (Party C works for 6 days): 2280× 7/ 120× (2+4) = 798 yuan.