$4)(18$ pts$)$ The demand equation for a piano by a certain piano maker can be approximated by $\backslash ($ p$=24-$x $\backslash )$ where $\backslash ($ p $\backslash )$ is the price $($in thousands of dollars$)$ per unit and $\backslash ($ x $\backslash )$ is the quantity of pianos demanded. Find and interpret the marginal revenue for the given production level. Interpret the answer in complete sentences. You must state what the marginal revenue means in laymen's terms. If you simply state that the marginal revenue is $\backslash (\backslash$$ $5000\backslash ),$ that is not an interpretation of the numerical answer.

a$)$ What is the marginal revenue at production level of $\backslash ($ x$=5\backslash )?$ Interpret the marginal revenue.

b$)$ Find the maximum revenue.