Solve the Problem $C ( x )$ , and the Revenue Function

Multiple Choice

Solve the problem.
-Given the cost function, $C ( x )$ , and the revenue function, $R ( x )$ , find the number of units $x$ that must be sold to brea
$$\begin{array} { l } C ( x ) = 7000 x + 63,000 \\R ( x ) = 14,000 x\end{array}$$

A) 11 units
B) 4 units
C) 9 units
D) 10 units en.