<PRE><B>Question 1091951</B>
&lt;br&gt;I will assume you are using the language in the way I am familiar with.&lt;br&gt;
In that case, if x units are produced and sold, then the cost is the cost per unit, multiplied by the number of units:&lt;br&gt;
{{{C(x) = (80+x)(x) = x^2+80x}}}&lt;br&gt;
The revenue is the selling price, multiplied by the number of units:&lt;br&gt;
{{{R(x) = 200x}}}&lt;br&gt;
The profit function is the difference between the revenue and cost:&lt;br&gt;
{{{P(x) = 200x - (x^2+80x) = -x^2+120x}}}&lt;br&gt;
And finally the marginal profit function is the derivative of the profit function:&lt;br&gt;
{{{-2x+120}}}
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