The marks awarded a student is determined by a bonus mark and the square of the number of questions answered correctly. For a student who answered 5 questions correctly, her mark was 52.5% and if she answered 3 questions correctly,the mark was 28.5%. Find an expression for the mark in terms of number of questions answered correctly ii. If the pass mark is 39%, find the number of questions a student must answer to pass. iii. find the mark scored by a student who answered six and half questions correctly.