The graph below shows the percentages of ingredients in a salad mix. A pie chart titled Percentages in salad mix. 40 percent is iceberg, 27 percent is romaine, 15 percent is spinach, 12 percent is arugula, 6 percent is carrots.

Dominic buys a 64-ounce container of salad mix. About how many ounces of romaine lettuce does the container have?
6 ounces
12 ounces
18 ounces
27 ounces