Since, Profit = Revenue – cost
Requirement is, profit > 0
\[C\left( x \right)\text{ }=\text{ }26,000\text{ }+\text{ }30\text{ }x;\]
where x is number of cassettes
\[\begin{array}{*{35}{l}}
\Rightarrow ~Profit\text{ }=\text{ }43x\text{ }\text{ }\left( 26,000\text{ }+\text{ }30x \right)\text{ }>\text{ }0 \\
\Rightarrow ~13x\text{ }\text{ }26,000\text{ }>\text{ }0 \\
\Rightarrow ~13x\text{ }>\text{ }26000 \\
\Rightarrow ~x\text{ }>\text{ }2000 \\
\end{array}\]
Therefore, the company should sell more than 2000 cassettes to realise profit.