A new car worth $$27,000$ is depreciating in value by $$3000$ per year. Complete parts $($a$)$ through $($c$).$

a$.$ Write a formula that models the car's value, $y,$ in dollars, after $x$ years.

b$.$ Use the formula from part $($a$)$ to determine after how many years the car's value will be $$12,000.$

c$.$ Graph the formula from part $($a$)$ in the first quadrant of a rectangular coordinate system. Then, show your solution to part $($b$)$ on the graph.