A convenience store sold 18 sodas one afternoon. Available sizes were 12, 16, and 20 ounce cups (small, medium, large). The total volume of soda sold was 336 oz. Total revenue was $48.The prices of the small, medium, and large sodas were $1, $2, and $3 respectively. How many of each size did the store sell? Let: x = the number of 12-oz sodas sold, y = the number of 16-oz sodas sold, and z = the number of 20-oz sodas sold.