Grade Calculator

#Auto Grader that converts students percentage into preset grades.
#Uses loops, variables, input and logic.
while True:
    print('You can calculate "Grade" or "Quit"')
    choice = input('What would you like to do? ')

    if choice == 'Grade':
        print('This application will calculate a students grade.')
        result = input ('Enter students exam percentage here...')
        if int (result) < 10:
            print('Students grade is calculated as: Unmarked')
        elif int (result) >=10 and int (result) <30:
            print('Students grade is calculated as: E')
        elif int (result) >=30 and int (result) <50:
            print('Students grade is calculated as: D')
        elif int (result) >=50 and int (result) <60:
            print('Students grade is calculated as: C')
        elif int (result) >=60 and int (result) <80:
            print('Students grade is calculated as: B')
        elif int (result) >=80 and int (result) <=100:
            print('Students grade is calculated as: A')

    elif choice == 'Quit':
        print ('Good Bye!')
        break

    else:
        print ('\nInvalid input!\n')