Question 577674
The profit, P,  would be the Revenue, R, minus the Cost, C.
{{{ P = R - C }}}
given:
{{{ C = x^2 + 100x + 500 }}}
{{{ R = 300x }}}
{{{ R - C = 300x - (x^2 + 100x + 500 ) }}}
and, since {{{ P = R - C }}},
{{{ P = 300x - x^2 - 100x - 500 }}}
{{{ P = -x^2 + 200x - 500 }}} 
where {{{x}}} is the number of items produced.
You can't really see what's going on until you
plot the function. Anywhere on the plot where
{{{P}}} is negative means that {{{ C }}} exceeds {{{ R }}}
and the company will soon go out of business.
here's the plot. {{{ P }}} is the vertical axis, 
{{{ x }}} is on the horizontal.
{{{ graph( 400, 400, -250, 250, -5000, 12000,  - x^2 + 200x - 500 ) }}}