SOLUTION
From the question,
The cost is given by the function
[tex]C(x)=2x+4[/tex]
And the price demand function is given by the function
[tex]p(x)=116-3x[/tex]
Now profit is calculated as
[tex]P(x)=xp(x)-C(x)[/tex]
So we have
[tex]\begin{gathered} P(x)=xp(x)-C(x) \\ P(x)=x(116-3x)-(2x+4) \\ =116x-3x^2-2x-4 \\ =-3x^2-114x-4 \end{gathered}[/tex]
Hence the profit function is
[tex]P(x)=-3x^2-114x-4[/tex]
At maximum profit, the derivative of the function for profit is equal to zero, we have
[tex]\begin{gathered} P(x)=-3x^2-114x-4 \\ P^{\prime}(x)=-6x^{}-114 \\ -6x^{}-114=0 \\ 6x=-114 \\ x=\frac{-114}{6} \\ x=-19 \end{gathered}[/tex]
So we can see that the answer to that is -19
The maximum profit becomes ,
we substitute x for -19, we have
[tex]\begin{gathered} P(-19)=-3x^2-114x-4 \\ P(-19)=-3(-19)^2-114(-19)-4 \\ =-1,083+2,166-4 \\ =1,079 \end{gathered}[/tex]
Hence the maximum profit is $1,079