6) In an engineering examination, a student is considered to have failed, secured second class, first class

and distinction, according as he scores less than 45%, between 45% and 60%, between 60% and 75% and

above 75% respectively. In a particular year 10% of the students failed in the examination and 5% of the

students get distinction. Find the % of students who have got first class and second class. (Assume the normal distribution)