A regression analysis between the number of cup of hot beverage sold (Y) and temperature of the day in degree Celsius (X) resulted in the following equation:

= 242 - 18X

The figure 18 in the equation implies that, on average,

(a)an increase of one degree Celsius in the temperature results in a decrease of 18 cups of hot beverage in sales.

(b)an increase of one degree Celsius in the temperature results in an increase of 18 cups of hot beverage in sales.

(c)a decrease of one degree Celsius in the temperature is correlated with a decrease of 18 cups of hot beverage in sales.

(d)18 cups of hot beverage were sold regardless of the temperature.