The Following Information Was Taken from the Inventory Records of Penelope

The following information was taken from the inventory records of Penelope Ltd.: $$\begin{array} { | l | l | } \hline \text { Dates } & \text { Inventory units } \\\hline \text { Inventory - Feb 1 } & 100 \text { units at } \$ 3.00 \\\hline \text { Purchases - April 1 } & 300 \text { units at } \$ 3.10 \\\hline \text { Purchases - July 15 } & 200 \text { units at } \$ 3.20 \\\hline \text { Units available for sale } & 600 \text { units } \\\hline & \\\hline \text { Sales - May 10 } & 200 \text { units at } \$ 6.00 \\\hline \text { Sales - November 15 } & 100 \text { units at } \$ 6.10 \\\hline\end{array}$$ What would be the gross margin, assuming that the weighted-average method is used in a periodic inventory system?

A) $310
B) $875
C) $935
D) $1,810