A student taking the S.T.E.P. maths exam asks of their friends also sitting the exam what they think they'll get on the first paper and takes the average, finding it to be 64. When the student adds their own predicted score to the sample the mean increase by 2 marks. An international friend then contacts this student to add their own predicted score, 90 marks, with the final average coming to 68 marks as a result. Hence find .
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E