We are given that the function of demand is given as:
![x=-8p+400](https://img.qammunity.org/2023/formulas/mathematics/college/1p6q0suh2jj4on6uo897felp0jlzjffgce.png)
Where:
![\begin{gathered} x=\text{ quantity demanded} \\ p=\text{ price} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/ogvmcuakqg1soematnn77w6a1kv5y11fno.png)
The function of revenue is given by:
![R=px=p\left(-8p+400\right)](https://img.qammunity.org/2023/formulas/mathematics/college/fomreu1ji03b6tdvmi9m8ua467acut7cmv.png)
Applying the distributive law we get:
![R=-8p^2+400p](https://img.qammunity.org/2023/formulas/mathematics/college/ain7a447wog7wexmlmw6wpvp2ryvp3e8zt.png)
We get an equation of the form:
![R=ap^2+bp+c](https://img.qammunity.org/2023/formulas/mathematics/college/a604e9af85rfco81owaoaddd28z5ulhpi4.png)
This is a quadratic equation and its graph is a parabola.
If the value of "a" is negative this means that the parabola opens downwards, therefore, the possible answers are A or D.
We notice that A is the graph of p vs R. Since our equation is a function of "p" we need R vs P, therefore, the right answer must be D.