(b) by definition and grading of offenses, to define the limits and systematize the exercise of discretion in punishment and to give fair warning of what is prohibited and of the consequences of violation;
(c) to prescribe penalties which are proportionate to the seriousness of offenses and which permit recognition of differences in rehabilitation possibilities among individual offenders;
(d) to safeguard conduct that is without guilt from condemnation as criminal and to condemn conduct that is with guilt as criminal;
(e) to prevent arbitrary or oppressive treatment of persons accused or convicted of offenses;
(f) to define the scope of federal interest in law enforcement against specific offenses and to systematize the exercise of federal criminal jurisdiction.