Three of these pairs of quantities are related by direct variation. which pair is not? a - x = hours traveled at 60 miles per hour, and y = total distance traveled b - x = length of a rectangular table, in inches, and y = length of the table, in centimeters c - x = number of $1-off coupons used, and y = amount saved d - x = time it takes to travel 60 miles, and y = speed traveled