10 obliged to impose the statutorily prescribed minimum sentence: and, if it does do so, it is required to enter its reasons for its decision on the record of the proceedings. (See Sv Nkosi supra at 141b-j; and S v Blaauw supra at 263e-264j.) [12] The effect of the provision is thus that s51(3)(b) automatically gives the sentencing court the discretion that it acquires under s51(3)(a) only where it finds substantial and compelling circumstances. It follows that the 'substantial and compelling' formula finds no application to offenders between 16 and 18. A court is therefore generally free to apply the usual sentencing criteria in deciding on an appropriate sentence for a child between the ages of 16 and 18. As in a case where s51(3)(a) finds application, the court in arriving at an appropriate sentence must, however, not lose sight of the fact that offences of the kind specified in Schedule 2 of the Act have been singled out by the legislature for severe sentences. The gravity of the offence must accordingly receive recognition in the determination of an appropriate sentence. [13] The Constitution, read with the various international instruments that have a bearing on the subject of the rights of young people in conflict with the law, furnishes the backdrop to this approach. Section 28(2) of the Constitution provides: '[A] child's best interests are of