會計pastpaper Q

06 #7
The club start selling rackets as from 1 Dec 2005. All purchases and sales were for cash. The rackets were sold at a profit of $20500 during the 4 months.
（sales of rackets is $48900, purchase of rackets is $30600)

我想問點揾amount of racket stock? Ans 話48900 - 20500 + 30600, 但係唔係應該48900 - ２８４００ + 30600　咩？
２８４００　係cost of original rackets(48900-20500=28400), 如果用番T account 揾，唔係應該48900 - ２８４００ + 30600　咩？