An instructor grades on a curve (normal distribution) and your grade for each test is determined by the following where S = your score.

A-grade: S + 2

B-grade: + S < + 2

C-grade: - S < +

D-grade: - 2 S < -

F-grade: S < 2

Using the grading scheme in the above problem, what is the range of scores for a C-gradeon a test if the average was = 75 and the standard deviation was = 6?

Greater than or equal to 87

Greater than or equal to 81 but less than 87

Greater than or equal to 69 but less than 81

Greater than or equal to 63 but less than 69