A Car Company Has Found That There Is a Linear $y=b+m x$

A car company has found that there is a linear relationship between the amount of money it spends on advertising and the number of cars it sells. When it spent 60,000 dollars on advertising, it sold 680 cars. Moreover, for each additional 5 thousand dollars spent, they sell 40 more cars. Let $y=b+m x$ be the formula for the number of cars sold as a function of $x$ , the amount of money spent on advertising. What is the practical interpretation of the vertical intercept of the equation?

A) The dollars spent on advertising per car sold.
B) The number of cars sold with no money spent on advertising.
C) The amount of advertising spent before any cars are sold.
D) The number of cars sold per dollar spent on advertising.