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Please find below logic which will help
Would you be able to share the sample file you are working with (if there is one)?
Consider transforming the table from a cross table to a straight table:
The Crosstable Load
basically creating a table with Student, Subject, Mark fields
Then use Max(Score) / Min(Score) and FirstSortedValue(Subject, -Score) / FirstSortedValue(Subject, Score) as expressions in a table chart with dimension Student.