6. Write a function Get_grade that takes a student's mark to determine the grade based on the table below, and returns the grade as a letter character. Write a function to validate the user's input to verify that it is within 0 to 100 marks. 80-100 65-79 50-64 A B C 40-49 0-39 D F Write a function Get_grade_point that takes the student's letter grade (i.e. A,B,C,D,F) as a char and returns the corresponding numerical grade point (4.0,3.0,2.0,1.0,0.0). Use a switch statement. Write the main program that includes the statements as follows. int mark; char grade; cout < > mark; cout