in the following equation = 30,000 + 3x with given sales ( in $500) and marketing (x in dollars), what does the equation imply?

a. An increase of $1 in marketing is associated with an increase of $31,500 in sales.

b. An increase of $1 in marketing is associated with an increase of $1,500 in sales.

c. An increase of $3 in marketing is associated with an increase of $31,500 in sales.

d. An increase of $3 in marketing is associated with an increase of $1,500 in sales.