This assumption reflects the real life that supplier usually visits a retailer randomly in a definite interval and the retailer shall replenish his stocks in accordance to the policy to control the replenishment up to a constant level.

• 这种背景代表这样的现实生活，供应者拜访零售商在一个时间段内的随机时刻，而零售商按照一个固定的补到水平控制策略补足库存。