现行条件下应收账款的信用成本=2400/360×40×60%×15%+2400×1%+10=58万元改变信用条件下应收账款的信用成本=-2400×10%×(1-60%)+2400×(1+10%)/360×60×60%×15%+2400×(1+10%)×2%+15=11.4万元应该延长信用期限
