(a) must
not be more than the sum of the maximum periods of imprisonment that could
have been imposed if separate sentences of imprisonment had been imposed in
respect of each offence to which the sentence relates, and
(b) must not be
less than the shortest term of imprisonment (if any) that must be imposed for
any separate offence or, if the sentence relates to more than one such
offence, must not be less than the shortest term of imprisonment that must be
imposed for any of the offences.
