#### Answer

$P(x)=200,000-50x$

#### Work Step by Step

Let $x$ be the manufacturing cost.The fixed cost of a phone is $200,000$. During each bicycle it costs $250$.
Selling price per phone = 300
Thus, the revenue function R(x) will be $R(x)=300x$
and
Cost function $C(x)=200,000+250x$
Amount of profit function $P(x)=R(x)-C(x)$
or, $P(x)=300x-(200,000+250x)$
Hence, $P(x)=200,000-50x$