Moon Uses a Periodic Inventory System with the Weighted Average

Moon uses a periodic inventory system with the weighted average method of cost assignment.The following data are available: $\begin{array}{ccc}\text { Date }& \text { Units Unit }& \text { Cost \$}\\\text { Jan } 6 \text { Beginning inventory } & 1000 & 10 \\15 \text { Purchase } & 2000 & 11 \\26 \text { Purchase } & 1000 & 12\\& 4000 \\31 \text { Sale } & 1000&20\\\text { Closing inventory }&3000\end{array}$ What is the value of cost of sales for January?

A) $10 000
B) $11 000
C) $12 000
D) $20 000