*WIP to take internal marks and external marks from user and print the Grade*
#internal marks out of 50 & external marks out of 100
#internal_marks >= 45 and external_marks >=90 --> Grade A
#internal_marks >= 40 and external_marks >=80 --> Grade B
#internal_marks >= 35 and external_marks >=70 --> Grade C
#internal_marks >= 20 and external_marks >=50 --> Grade D
#internal_marks >= 15 and external_marks >= 30 --> Grade E
#Otherwise Grade F