After surveying students in her homeroom, Katie decided to use a number cube to predict the probability that a randomly chosen student in her school planned to stay after school today for extracurricular activities. In Katie’s simulation, a roll of 1 represents staying after school, while rolls of 2, 3, 4, 5, or 6 represent leaving school at the end of classes.According to Katie’s model, what is the probability that three randomly chosen students will all stay after school for extracurricular activities today?