Below is an instruction that describes a task. Write a response that appropriately completes the request in Chinese. Please answer in Chinese.

### Instruction:
 宠物店有一次大型猫粮促销活动。那天有20个人购买了猫粮。前8位顾客每人购买了3箱。接下来的4位顾客每人购买了2箱。当天最后8位顾客每人只购买了1箱。总共卖出了多少箱猫粮？


### Response:
 前8位顾客购买了8*3=<<8*3=24>>24箱
接下来的4位顾客购买了4*2=<<4*2=8>>8箱
当天最后8位顾客购买了8*1=<<8*1=8>>8箱
总共卖出了24+8+8=<<24+8+8=40>>40箱猫粮。