$2.$ The table below shows the supply and demand conditions for a firm that will play trumpets on the streets when requested.

$\backslash$begin$\{$tabular$\}\{|$l$|$l$|$l$|$l$|\}$

$\backslash$hline Price & Quantity Demanded & Quantity Supplied & Social Cost $($Supply $+$ External Cost$)\backslash \backslash$

$\backslash$hline$\backslash (\backslash$$ $30\backslash )$ & $10$ & $105$ & $70\backslash \backslash$

$\backslash$hline$\backslash (\backslash$$ $25\backslash )$ & $20$ & $90$ & $55\backslash \backslash$

$\backslash$hline$\backslash (\backslash$$ $20\backslash )$ & $40$ & $75$ & $40\backslash \backslash$

$\backslash$hline$\backslash (\backslash$$ $15\backslash )$ & $60$ & $60$ & $25\backslash \backslash$

$\backslash$hline$\backslash (\backslash$$ $10\backslash )$ & $80$ & $45$ & $15\backslash \backslash$

$\backslash$hline$\backslash (\backslash$$ $5\backslash )$ & $100$ & $30$ & $5\backslash \backslash$

$\backslash$hline

$\backslash$end$\{$tabular$\}$

a$.$ Describe the negative externality in this situation.

b$.$ Identify the equilibrium price and quantity when we account only for private costs.

c$.$ Why is this outcome inefficient?

d$.$ Identify the equilibrium price and quantity if we account for social costs $($also known as the socially optimal price and quantity$).$