def solution(self):
        """Returns the answer to a given problem"""
        num = self.num

        solution_file = os.path.join(EULER_DATA, 'solutions.txt')
        solution_line = linecache.getline(solution_file, num)

        try:
            answer = solution_line.split('. ')[1].strip()
        except IndexError:
            answer = None

        if answer:
            return answer
        else:
            msg = 'Answer for problem %i not found in solutions.txt.' % num
            click.secho(msg, fg='red')
            click.echo('If you have an answer, consider submitting a pull '
                       'request to EulerPy on GitHub.')
            sys.exit(1)
Returns the answer to a given problem