The marks of students on a statistics exam are normally dist

The marks of students on a statistics exam are normally distributed with a mean fo 80 and standard deviation of 10. The examination board decided to place the top 10 percent of the students in Grade A, the next 20 percent in Grade B, the next 40 percent in Grade C, the next 20 percent in Grade D, and the bottom 10 percent in Grade F (failure). What marks should a student get to obtain an A grade? What marks should a student get to obtain C or better?

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