d. Experiment with backtracking and the cut operator (!) to control program flow and improve efficiency.

 

grade(Mark, 'A+') :- Mark >= 80, !.

grade(Mark, 'A') :- Mark >= 70, !.

grade(Mark, 'A-') :- Mark >= 60, !.

grade(Mark, 'B') :- Mark >= 50, !.

grade(_, 'F').

go :-

    write("Enter Your Mark: "),

    read(A),

    grade(A, Grade),

    write("Your grade: "), nl,

    write(Grade).