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: $\hat { y }$ = 50,000 + 6x ?
The above equation implies that an increase of _____.

A) $6 in advertising is associated with an increase of $6,000 in sales
B) $1 in advertising is associated with an increase of $6 in sales
C) $1 in advertising is associated with an increase of $56,000 in sales
D) $1 in advertising is associated with an increase of $6,000 in sales