The total revenue and total cost functions for the production and sale of $x$ TV's are given as $$R(x) = 120 x - 0.2 x^2$$ and $$C(x) = 3570 + 21 x.$$
(A) Find the value of $x$ where the graph of $R(x)$ has a horizontal tangent line. $x$ values is
(B) Find the profit function in terms of $x$.
$P(x)$ =
(C) Find the value of $x$ where the graph of $P(x)$ has a horizontal tangent line.
$x$ values =
(D) List all the $x$ values of the break-even point(s).
If there are no break-even points, enter 'NONE'.
List of $x$ values =