Penelope loves to travel and sets aside a budget every year for her vacations. Among her circle of friends, the average annual vacation budget is $3,000 with a standard deviation of $400. Last year, Penelope spent $3,500 on her vacations. What is Penelope's last year's vacation expenses z -score? Use the following formula to calculate z -score: z is equal to the fraction with numerator x minus mu and denominator sigma where x is the data point, mu is the mean, and σ is the standard deviation.