Sadie has worked at a cell phone store for nine months. Her sales are denoted by the set {5, 7, 8, 21, 15, 18, 5, 13, 14}. Which five-number summary represents the data set?

{5, 6, 13, 16.5, 21}
{5, 14.5, 15, 9, 14}
{5, 7, 13, 16, 21}
{5, 7, 13, 15, 18}