Use the following to answer the given question
\(\begin{array}{c|c} & N \\ \hline \text{Stock 1/1/93} & 4,500 \\ Sales & 13,500\\ Purchases & 5,000 \\ \text{Carriage inwards} & 500 \\ \text{Stock 31/12/93} & 4,200 \\ \text{Return inwards} & 600\end{array}\)
Cost of sales is