A regression analysis between sales (y in $1000) and advertising (x in dollars) resulted in the following equation y = 50,000 + 6x.
The above equation implies that an:

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