boundary value testing

Consider a function called grading, with the following requirement specification: The function is passed an exam mark (out of 80) and a coursework mark (out of 20), from which it generates a grade for the course in the range 'A' to 'D'. The grade is calculated from the overall mark which is calculated as the sum of the exam and coursework marks, as follows: greater than or equal to 90 greater than or equal to 70, but less than 90- 'B' greater than or equal to 50, but less than 70- 'C' less than 50 Where a mark is outside its expected range then a proper fault message is generated. All inputs are passed as integers. The code of this method is: Deskase exas; public class First rublas stcios ecodingint marke, int mark20) int total mark20 + markio; Strins output if (total 390) output "A" else if ((total 70) 88 (total 9)) outout. ""; else (total) 50) 86 (total 20% output="0" alss outout" 3.a-) Write the test cases based on Normal Boundary Value Testing technique. 3.6-) Write the additional test cases when Robust Boundary Value Testing is applied