*@return total marks (0 if 0 assessments) public double getTotal() 5 double result; return 0 *@return average marks (null if 0 assessments) public Double getAverage() { return null; //to be completed @param assessmentNumber *@return true if assessmentNumber is valid, false otherwise. For example if there were 5 assessments, the valid assessment numbers are from 0 to 4 (including 0 and 4) public boolean isValidAssessmentNumber(int assessmentNumber) ( return false; //to be completed *@param assessmentNumber *@return mark in assessment with given index return null 1f no such assessment exISTS public Double getMark(int assessmentNumber) { return null; //to be completed