The grades on an examination whose mean is 525 and whose standard deviation is 80 are normally

Question:

The grades on an examination whose mean is 525 and whose standard deviation is 80 are normally distributed.
a. Anyone who scores below 350 will be retested. What percentage does this represent?
b. The top 12% are to receive a special commendation. What score must be surpassed to receive this special commendation?
c. The interquartile range of a is the difference between Q1 and Q3, Q3 - Qx. Find the interquartile range for the grades on this examination.
d. Find the grade such that only 1 out of 500 will score above it.
Distribution
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