Write a shell script "Sgrade" to generate a mark sheet of a student. to generate a mark sheet of a student. Take marks for 3 subjects, calculate and display total marks, percentage, and a letter grade obtained by the student based on the percentage. A letter grade is computed from percentage using the following scale: 95-100 A+ 90-94 A 80-89 B 70-79 C 65-69 D 0-64 F.