Answer
$2000$ units
Work Step by Step
Cost $=$ Variable cost $+$ Fixed cost
If $R(x)$ is the revenue from selling $x$ items at a price of m each, then
$R$ is the linear function $R(x)=mx$ .
Profit $=$ Revenue-Cost,$\qquad P(x)=R(x)-C(x)$
Breakeven occurs when $P=0$, or $R(x)=C(x)$.
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We first express $R(x)=5x$
Since Variable cost = $0.30\cdot R(x)=0.3(5x)=1.5x$,
the Cost function is
$C(x)=1.5x+7000$
Breakeven$: R(x)=C(x)$
$5x=1.5x+7000\qquad/-1.5x$
$3.5x=7000\qquad/\div 3.5$
$x=2000$
To break even, there should be
$2000$ units sold
