订购量为4千张时获利的期望值: EC(4)=-16002×0.05 +500×010+600×0.25 +1700×0.35+2800×015 +2800×0.10 =1315元)订购量为4千张时获利的期望值： • E[C(4)]=(-1600)×0.05 +(-500)×0.10+600×0.25 +1700×0.35+2800×0.15 +2800×0.10 =1315(元)