Mikayla and Mackenzie began arguing about who did better on their tests, but they couldn't decide who did better given that they took different tests. Mikayla took a test in Science and earned a 75, and Mackenzie took a test in Social Studies and earned a 69.2. Use the fact that all the students' test grades in the Science class had a mean of 71.2 and a standard deviation of 10, and all the students' test grades in Social Studies had a mean of 60.9 and a standard deviation of 8.6 to answer the following questions.

a) Calculate the z-score for Mikayla's test grade.

b) Calculate the z-score for Mackenzie's test grade.

c) Which person did relatively better?

i. Mikayla

ii. Mackenzie

iii. They did equally well