A restaurant investigated the correlation between prices and the number of customers. The linear model below represents this situation, where x is the average meal price [in dollars], and y is the number of daily customers. Interpret the slope. A. The average number of daily customers is 18. B. The average price per meal is $18. C. If the average meal price decreases by $1, the number of daily customers decreases by 18. D. If the average meal price increases by $1, the number of daily customers decreases by 18.