The Following Data Pertain to Activity and Costs for Two

The following data pertain to activity and costs for two months:
$\begin{array}{|l|r|r|} \hline& \text { October } & \text { November } \\\hline \text { Activity level in units } & 5,000 & 10,000 \\\hline \text { Variable costs } & \$ 10,000 & ? \\\hline \text { Fixed costs } & 30,000 & ? \\\hline \text { Mixed costs } & 20,000 & ? \\\hline \text { Total costs } & \$ 60,000 & \$ 75,000 \\\hline\end{array}$
Assuming that these activity levels are within the relevant range,what were the mixed costs for November?

A) $20,000.
B) $25,000.
C) $35,000.
D) $40,000.