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
$$\begin{array} { l } C ( x ) = 1.3 x + 840 \\R ( x ) = 1.9 x\end{array}$$

A) 1400 units
B) 1420 units
C) 337 units
D) 1410 units en.