In case of which soft drink was the average annual sale minimum during the period 1988-1993?

$$\eqalign{ & \text{Average annual sales of Dew-drop} \cr & = \frac{10 + 15 + 15 + 15 + 30 + 25}{6} \cr & = \frac{110}{6} \cr & = 18.3 \text{ lakh bottles} \cr & \text{Average sales of Cool-up} \cr & = \frac{120}{6} \cr & = 20 \text{ lakh bottles} \cr & \text{So, minimum sales = Dew-drop} \cr} $$