We would like to examine whether there is evidence that the true mean amount spent on bus tickets by U of M students in one month is greater than $90. Bus ticket expenses (per month) are known to follow a normal distribution. A random sample of 36 students is selected. The mean and standard deviation of the amount spent on bus tickets for one month for these 36 students are calculated to be $89 and $5, respectively. What is the test statistic for the appropriate hypothesis test? a.t = -2.4 b.z = -1.2 c.z = 1.2 d.t = 2.4 e.t = -1.2