问题如下图：
选项：
A. 
B. 
C. 
解释：
错了吧？？？-21才对啊
NO.PZ2018062018000036 问题如下 Accorng to the following information, the cash paito supplier is: A.13 B.16 C.27 A is correct.-Cash paito suppliers= -COGS-△Inv+△AP= -20-(20-24)+(33-30)= -13. 这道题是不是老师讲的用两个等式计算，一是 INVb+purchase-COGS=INVe ，求purchase二是 purchase+AP的流动量但我算出来结果不对，请老师再指点一下，谢谢
NO.PZ2018062018000036 问题如下 Accorng to the following information, the cash paito supplier is: A.13 B.16 C.27 A is correct.-Cash paito suppliers= -COGS-△Inv+△AP= -20-(20-24)+(33-30)= -13. 老师可能课上讲了，但是麻烦老师再讲解下，为什么没有计算AR
NO.PZ2018062018000036 问题如下 Accorng to the following information, the cash paito supplier is: A.13 B.16 C.27 A is correct.-Cash paito suppliers= -COGS-△Inv+△AP= -20-(20-24)+(33-30)= -13. 如题
NO.PZ2018062018000036 16 27 A is correct. -Cash paito suppliers= -COGS-△Inv+△AP= -20-(20-24)+(33-30)= -13.如题，为何不是16？？？
NO.PZ2018062018000036 不明白为什么用期末减期初
