A Regression Analysis Between Sales Y in $1000) and Advertising $\hat { Y }$

A regression analysis between sales Y in $1000) and advertising X in dollars) resulted in the following equation $\hat { Y }$ = 30,000 + 4 X
The above equation implies that an

A) increase of $4 in advertising is associated with an increase of $4,000 in sales
B) increase of $1 in advertising is associated with an increase of $4 in sales
C) increase of $1 in advertising is associated with an increase of $34,000 in sales
D) increase of $1 in advertising is associated with an increase of $4,000 in sales