It is common for businesses to adjust their prices according to demand. when whites rentals charges $40 a day for a bike rental, the company expects to rent 60 bikes that day. for every $2 reduction in the cost of the rental, the company can expect another 5 rentals for the day. the revenue for any day is represented by the function r(x)=(60 + 5x)(40+2x), where x is the number of $2 decreases in charge. This function represents:
a. A linear relationship between price decrease and revenue
b. A quadratic relationship between price decrease and revenue
c. A direct correlation between price decrease and increased rentals
d. An inverse relationship between price decrease and rentals