(a) The following are marks for 99 students in a statistics exam Marks Number of students 0-10 10 10-20 ? 20-30 25 30-40 30 40-50 ? 50-60 10 On later analysis, It was discovered that two class interval frequencies were missing. The median score was found to be 30. (i) Find the missing frequencies (3marks) (ii) Determine the upper quartile mark of the students