Sarah sets her alarm for 6:30 AM to make sure she gets to class on time. Based on past experience, she knows that she gets up before her alarm rings 10% of the time, gets up right when her alarm rings 30% of the time, hits snooze once 20% of the time and hits snooze twice 20% of the time. The remaining proportion of times, she turns off her alarm when it rings and ends up arriving late to.